diff --git a/.env.example b/.env.example
index ed6d4bc..7cfda67 100644
--- a/.env.example
+++ b/.env.example
@@ -4,6 +4,34 @@
 # Copy this file to .env and fill in the values
 # DO NOT commit .env to version control
 
+# ===========================================================================
+# Docker Image Versions (Centralized Version Management)
+# ===========================================================================
+# All Docker image versions in one place for easy updates and consistency.
+# Update these versions when upgrading services.
+#
+# Core Infrastructure:
+VAULT_VERSION=1.18
+POSTGRES_VERSION=18
+MYSQL_VERSION=8.0.40
+MONGODB_VERSION=7.0
+REDIS_VERSION=7.4-alpine3.21
+RABBITMQ_VERSION=3.13-management-alpine
+
+# Connection Pooling:
+PGBOUNCER_VERSION=latest
+
+# Git Server:
+FORGEJO_VERSION=1.21.11-0
+
+# Observability Stack:
+PROMETHEUS_VERSION=v2.48.0
+GRAFANA_VERSION=10.2.2
+LOKI_VERSION=2.9.3
+VECTOR_VERSION=0.50.0-debian
+CADVISOR_VERSION=v0.47.2
+REDIS_EXPORTER_VERSION=v1.55.0
+
 # ===========================================================================
 # HashiCorp Vault Configuration (Secrets Management & PKI)
 # ===========================================================================
diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index 9fd6444..e5f485d 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -92,20 +92,62 @@ jobs:
           done
         continue-on-error: true
 
-      - name: Check Docker image vulnerabilities
+      - name: Scan Docker images for vulnerabilities
         run: |
+          echo "Installing Trivy for Docker image scanning..."
+          curl -sfL https://raw.githubusercontent.com/aquasecurity/trivy/main/contrib/install.sh | sh -s -- -b /usr/local/bin v0.58.0
+
+          echo ""
           echo "Extracting Docker images from docker-compose.yml..."
 
-          # Get unique images from docker-compose.yml
-          images=$(grep -E "^\s+image:" docker-compose.yml | awk '{print $2}' | sort -u)
+          # Get unique images from docker-compose.yml (resolve env vars to defaults)
+          images=$(grep -E "^\s+image:" docker-compose.yml | \
+            sed 's/.*image:\s*//' | \
+            sed 's/\${[^:]*:-\([^}]*\)}/\1/g' | \
+            sort -u)
 
           echo "Found images:"
           echo "$images"
           echo ""
-          echo "Note: For full vulnerability scanning, consider using:"
-          echo "  - Trivy: trivy image <image>"
-          echo "  - Snyk: snyk container test <image>"
-          echo "  - Docker Scout: docker scout cves <image>"
+
+          vuln_count=0
+          critical_count=0
+
+          for image in $images; do
+            echo ""
+            echo "=========================================="
+            echo "Scanning: $image"
+            echo "=========================================="
+
+            # Scan for CRITICAL and HIGH vulnerabilities
+            if ! trivy image --severity CRITICAL,HIGH --no-progress --exit-code 0 "$image" 2>/dev/null; then
+              echo "⚠ Warning: Could not scan $image (may need to be pulled first)"
+              continue
+            fi
+
+            # Count critical vulnerabilities
+            critical=$(trivy image --severity CRITICAL --no-progress --format json "$image" 2>/dev/null | \
+              jq '[.Results[]?.Vulnerabilities // [] | length] | add // 0' 2>/dev/null || echo "0")
+
+            if [ "$critical" -gt 0 ]; then
+              echo "⚠ Found $critical CRITICAL vulnerabilities in $image"
+              critical_count=$((critical_count + critical))
+            fi
+
+            vuln_count=$((vuln_count + 1))
+          done
+
+          echo ""
+          echo "=========================================="
+          echo "Scan Summary"
+          echo "=========================================="
+          echo "Images scanned: $vuln_count"
+          echo "Total CRITICAL vulnerabilities: $critical_count"
+
+          if [ "$critical_count" -gt 0 ]; then
+            echo ""
+            echo "⚠ Warning: Critical vulnerabilities found. Review and update affected images."
+          fi
 
   trivy-scan:
     name: Trivy Security Scan
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index e75756b..24dea49 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -243,6 +243,65 @@ jobs:
             echo "ℹ No Python files to validate"
           fi
 
+  unit-tests:
+    name: Unit Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: '3.11'
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version-file: 'reference-apps/golang/go.mod'
+
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Install Python test dependencies
+        run: |
+          pip install pytest pytest-asyncio pytest-cov pytest-mock httpx
+
+      - name: Run FastAPI unit tests
+        run: |
+          cd reference-apps/fastapi
+          pip install -r requirements.txt
+          # Run tests that don't require external services
+          pytest tests/ -v --ignore=tests/test_integration.py -k "not integration" \
+            --tb=short || echo "⚠ Some tests require running services (expected in CI)"
+        continue-on-error: true
+
+      - name: Run Go unit tests
+        run: |
+          cd reference-apps/golang
+          go test -v -short ./... 2>&1 || echo "⚠ Some tests require running services (expected in CI)"
+        continue-on-error: true
+
+      - name: Run Rust unit tests
+        run: |
+          cd reference-apps/rust
+          cargo test --lib -- --test-threads=1 2>&1 || echo "⚠ Some tests require running services (expected in CI)"
+        continue-on-error: true
+
+      - name: Test summary
+        run: |
+          echo "=========================================="
+          echo "Unit Test Summary"
+          echo "=========================================="
+          echo ""
+          echo "Note: Full test coverage requires running infrastructure services."
+          echo "Unit tests that don't require external dependencies were executed."
+          echo ""
+          echo "For full integration tests, run locally with:"
+          echo "  ./devstack start --profile standard"
+          echo "  ./tests/run-all-tests.sh"
+
   integration-test:
     name: Integration Test (Basic)
     runs-on: ubuntu-latest
@@ -333,21 +392,60 @@ jobs:
       - validate-configs
       - test-documentation
       - test-python
+      - unit-tests
       - integration-test
     if: always()
 
     steps:
       - name: Check test results
         run: |
-          if [ "${{ needs.validate-compose.result }}" != "success" ] || \
-             [ "${{ needs.validate-env.result }}" != "success" ] || \
-             [ "${{ needs.validate-scripts.result }}" != "success" ] || \
-             [ "${{ needs.validate-configs.result }}" != "success" ] || \
-             [ "${{ needs.test-documentation.result }}" != "success" ] || \
-             [ "${{ needs.test-python.result }}" != "success" ] || \
-             [ "${{ needs.integration-test.result }}" != "success" ]; then
-            echo "❌ Some tests failed"
+          failed=0
+
+          if [ "${{ needs.validate-compose.result }}" != "success" ]; then
+            echo "❌ Docker Compose validation failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.validate-env.result }}" != "success" ]; then
+            echo "❌ Environment validation failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.validate-scripts.result }}" != "success" ]; then
+            echo "❌ Script validation failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.validate-configs.result }}" != "success" ]; then
+            echo "❌ Config validation failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.test-documentation.result }}" != "success" ]; then
+            echo "❌ Documentation tests failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.test-python.result }}" != "success" ]; then
+            echo "❌ Python syntax check failed"
+            failed=1
+          fi
+
+          if [ "${{ needs.integration-test.result }}" != "success" ]; then
+            echo "❌ Integration tests failed"
+            failed=1
+          fi
+
+          # Unit tests are informational (some require services)
+          if [ "${{ needs.unit-tests.result }}" == "failure" ]; then
+            echo "⚠ Unit tests had failures (some may require running services)"
+          fi
+
+          if [ $failed -eq 1 ]; then
             exit 1
           fi
 
-          echo "✅ All tests passed!"
+          echo "✅ All validation tests passed!"
+          echo ""
+          echo "Note: Unit tests for reference apps may have partial failures"
+          echo "when external services are not available. This is expected in CI."
diff --git a/configs/forgejo/Dockerfile b/configs/forgejo/Dockerfile
index 98cc06c..a2cc025 100644
--- a/configs/forgejo/Dockerfile
+++ b/configs/forgejo/Dockerfile
@@ -1,4 +1,5 @@
-FROM codeberg.org/forgejo/forgejo:1.21.11-0
+ARG FORGEJO_VERSION=1.21.11-0
+FROM codeberg.org/forgejo/forgejo:${FORGEJO_VERSION}
 
 # Install dependencies for Vault integration (needs root)
 USER root
diff --git a/configs/pgbouncer/Dockerfile b/configs/pgbouncer/Dockerfile
index 7cb07e3..a9dea11 100644
--- a/configs/pgbouncer/Dockerfile
+++ b/configs/pgbouncer/Dockerfile
@@ -1,4 +1,5 @@
-FROM edoburu/pgbouncer:latest
+ARG PGBOUNCER_VERSION=latest
+FROM edoburu/pgbouncer:${PGBOUNCER_VERSION}
 
 # Install dependencies for Vault integration
 USER root
diff --git a/configs/vector/Dockerfile b/configs/vector/Dockerfile
index 767b548..9c3fc95 100644
--- a/configs/vector/Dockerfile
+++ b/configs/vector/Dockerfile
@@ -1,4 +1,5 @@
-FROM timberio/vector:0.50.0-debian
+ARG VECTOR_VERSION=0.50.0-debian
+FROM timberio/vector:${VECTOR_VERSION}
 
 # Install dependencies required by init script
 RUN apt-get update && \
diff --git a/docker-compose.yml b/docker-compose.yml
index 853911d..1df73fc 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -31,7 +31,7 @@ x-init-library: &init-library
 # =============================================================================
 x-redis-common: &redis-common
   <<: *default-platform
-  image: redis:7.4-alpine3.21
+  image: redis:${REDIS_VERSION:-7.4-alpine3.21}
   restart: unless-stopped
   entrypoint: ["/init/init-approle.sh"]
   environment: &redis-env
@@ -75,7 +75,7 @@ x-redis-common: &redis-common
 # =============================================================================
 x-redis-exporter-common: &redis-exporter-common
   <<: *default-platform
-  image: oliver006/redis_exporter:v1.55.0
+  image: oliver006/redis_exporter:${REDIS_EXPORTER_VERSION:-v1.55.0}
   restart: unless-stopped
   entrypoint: ["/init/init.sh"]
   environment: &redis-exporter-env
@@ -178,7 +178,7 @@ services:
 
   postgres:
     <<: *default-platform
-    image: postgres:18
+    image: postgres:${POSTGRES_VERSION:-18}
     container_name: dev-postgres
     restart: unless-stopped
 
@@ -270,7 +270,10 @@ services:
   
   pgbouncer:
     <<: *default-platform
-    build: ./configs/pgbouncer
+    build:
+      context: ./configs/pgbouncer
+      args:
+        PGBOUNCER_VERSION: ${PGBOUNCER_VERSION:-latest}
     container_name: dev-pgbouncer
     restart: unless-stopped
 
@@ -336,7 +339,7 @@ services:
 
   mysql:
     <<: *default-platform
-    image: mysql:8.0.40
+    image: mysql:${MYSQL_VERSION:-8.0.40}
     container_name: dev-mysql
     restart: unless-stopped
 
@@ -527,7 +530,7 @@ services:
 
   rabbitmq:
     <<: *default-platform
-    image: rabbitmq:3.13-management-alpine
+    image: rabbitmq:${RABBITMQ_VERSION:-3.13-management-alpine}
     container_name: dev-rabbitmq
     restart: unless-stopped
 
@@ -591,7 +594,7 @@ services:
   
   mongodb:
     <<: *default-platform
-    image: mongo:7.0
+    image: mongo:${MONGODB_VERSION:-7.0}
     container_name: dev-mongodb
     restart: unless-stopped
 
@@ -658,7 +661,10 @@ services:
   
   forgejo:
     <<: *default-platform
-    build: ./configs/forgejo
+    build:
+      context: ./configs/forgejo
+      args:
+        FORGEJO_VERSION: ${FORGEJO_VERSION:-1.21.11-0}
     container_name: dev-forgejo
     restart: unless-stopped
 
@@ -731,7 +737,7 @@ services:
 
   vault:
     <<: *default-platform
-    image: hashicorp/vault:1.18
+    image: hashicorp/vault:${VAULT_VERSION:-1.18}
     container_name: dev-vault
     restart: unless-stopped
 
@@ -1147,7 +1153,7 @@ services:
 
   prometheus:
     <<: *default-platform
-    image: prom/prometheus:v2.48.0
+    image: prom/prometheus:${PROMETHEUS_VERSION:-v2.48.0}
     container_name: dev-prometheus
     restart: unless-stopped
 
@@ -1207,7 +1213,7 @@ services:
 
   grafana:
     <<: *default-platform
-    image: grafana/grafana:10.2.2
+    image: grafana/grafana:${GRAFANA_VERSION:-10.2.2}
     container_name: dev-grafana
     restart: unless-stopped
 
@@ -1267,7 +1273,7 @@ services:
 
   loki:
     <<: *default-platform
-    image: grafana/loki:2.9.3
+    image: grafana/loki:${LOKI_VERSION:-2.9.3}
     container_name: dev-loki
     restart: unless-stopped
 
@@ -1402,7 +1408,7 @@ services:
 
   cadvisor:
     <<: *default-platform
-    image: gcr.io/cadvisor/cadvisor:v0.47.2
+    image: gcr.io/cadvisor/cadvisor:${CADVISOR_VERSION:-v0.47.2}
     container_name: dev-cadvisor
     restart: unless-stopped
 
@@ -1458,7 +1464,10 @@ services:
 
   vector:
     <<: *default-platform
-    build: ./configs/vector
+    build:
+      context: ./configs/vector
+      args:
+        VECTOR_VERSION: ${VECTOR_VERSION:-0.50.0-debian}
     container_name: dev-vector
     restart: unless-stopped