Add HTTP Range requests and streaming support for /{id}/data endpoints

[nikooo777]

@shyba and I are not fluent in Erlang, so pardon us if slop is spotted!
we'll try our best to clean it up during review.

Why

• Prevent OOM and long latency when serving large data via /{id}/data.
• Add HTTP Range support for media/partial reads.
• Preserve HTTPSig semantics for streamed responses.

What's Included

• Range requests for /{id}/data and /tx/{id}/data
  • Parses Range (bytes=start-end | start- | -suffix).
  • Returns correct 206 with Content‑Range and Accept‑Ranges, or 416 with bytes */total.
  • Small ranges are buffered and fully signed (includes Content‑Digest); large ranges stream.
• Memory‑efficient streaming
  • Large full GETs and large ranges stream via chunked transfer encoding.
  • Open‑ended ranges (bytes=start-) stream chunk‑by‑chunk; no unbounded buffering.
  • Streamed responses are header‑signed (status + ao-result).
• Storage‑agnostic reader
  • New hb_data_reader: HEAD‑based metadata discovery with Range fallback; read_range/stream helpers.
  • New hb_http_range: Range parsing and Content‑Range builders.
• HTTP server integration
  • hb_http_server intercepts data endpoints, decides buffer vs. stream based on size threshold.
  • Adds reply_streamed[_signed]/send_streamed_response in hb_http.
• HTTPSig improvements
  • dev_codec_httpsig: components serialization now directly uses hb_message:convert (fixes badmatch, normalizes headers/body for tests).
• Defaults and config
  • hb_opts adds:
    • streaming_threshold (10MB)
    • stream_chunk_size (1MB)
    • range_default_content_type (application/octet-stream)
    • range_requests_enabled (true).
    • stream_signature (off | header)
  • Streaming is disabled unless you opt in.
• Minor cleanup: rebar.config dedup.

Notes

• Buffered responses (small ranges/small full GETs): standard HTTPSig response with Content‑Digest.
• Streamed responses (large full or large ranges): header‑only HTTPSig;
• CORS headers preserved; Accept‑Ranges: bytes always set for data endpoints.