feat(voice-detect): wire backend into index, gallery and build

Register the voice-detect.cpp speaker-recognition + voice-analysis
backend (added in Voice-INT-A) into LocalAI's distribution surfaces,
mirroring the ced backend (the closest mudler C++/ggml audio analogue):

- backend/index.yaml: add the &voicedetect meta-backend (capabilities
  platform map, no top-level uri) plus the full set of concrete per-arch
  image entries (cpu/cuda12/cuda13/metal/rocm/sycl/vulkan/l4t and the
  -development variants). Referential integrity audited - every alias
  target resolves.
- gallery/index.yaml: add 5 model entries on backend voice-detect -
  ECAPA-TDNN, WeSpeaker ResNet34, 3D-Speaker ERes2Net, CAM++ and the
  wav2vec2 age/gender/emotion analyze model. The engine architecture is
  read from GGUF metadata (voicedetect.arch) at load. GGUF artifacts are
  not yet published: each files: entry points at the intended
  mudler/voice-detect-gguf location with a TODO to fill sha256 after
  upload (no fabricated hashes).
- .github/backend-matrix.yml: add the linux build matrix block + the
  darwin metal entry mirroring ced.
- .github/workflows/bump_deps.yaml: track mudler/voice-detect.cpp via
  VOICEDETECT_VERSION (pin 47546430, = 4754643).
- core/config/backend_capabilities.go: register voice-detect in the
  backend capability map (VoiceVerify/VoiceEmbed/VoiceAnalyze ->
  speaker_recognition), mirroring speaker-recognition.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:claude-opus-4-8 [Claude Code]

.github/workflows/bump_deps.yaml

@@ -46,6 +46,10 @@ jobs:
             variable: "CED_VERSION"
             branch: "master"
             file: "backend/go/ced/Makefile"
+          - repository: "mudler/voice-detect.cpp"
+            variable: "VOICEDETECT_VERSION"
+            branch: "master"
+            file: "backend/go/voice-detect/Makefile"
           - repository: "mudler/depth-anything.cpp"
             variable: "DEPTHANYTHING_VERSION"
             branch: "master"