fix(docker): drop voice deps from runtime image to unblock 3.14 build

CI broke on the build job: kokoro's resolver walks back to a version
that pins numpy<2, which has no cp314 wheel; pip falls back to compiling
numpy from source; python:3.14-slim has no compiler; build fails.

Removing the voice deps install (torch + faster-whisper + kokoro +
soundfile + spacy) from the runtime image:
- unblocks the 3.14 build immediately
- shrinks the image by ~2 GB (torch alone)
- aligns with the explicit operator preference (voice/TTS doesn't pay
  off in their workflow; conversational chat will get smaller/faster
  with the new no-tools chat model on GPU, so transcription matters
  even less)

Voice paths in code are already lazily guarded — TYPE_CHECKING-only
imports plus try/except inside load_stt_model. With VOICE_ENABLED=false
(default), the app starts cleanly with no voice deps installed. With
voice enabled, the import error is caught and logged; the feature
degrades gracefully rather than crashing.

To re-enable voice in a future build, `pyproject.toml` already has the
`voice` extra ready: install it with `pip install .[voice]` plus the
torch index pin, and download spacy en_core_web_sm. Dockerfile comment
documents the path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -16,12 +16,14 @@ COPY pyproject.toml .
 COPY src/ src/
 RUN --mount=type=cache,target=/root/.cache/pip \
     pip install .
-# Voice dependencies (faster-whisper, Kokoro TTS, soundfile) — activated at runtime via VOICE_ENABLED
-# Install CPU-only torch first so pip doesn't pull full CUDA wheels (~2 GB) for kokoro/transformers.
-RUN --mount=type=cache,target=/root/.cache/pip \
-    pip install torch --index-url https://download.pytorch.org/whl/cpu \
-    && pip install faster-whisper kokoro soundfile \
-    && python -m spacy download en_core_web_sm
+
+# Voice deps (faster-whisper, kokoro, torch, soundfile, spacy) are NOT
+# installed in the production image. They added ~2 GB and pulled numpy<2,
+# which has no cp314 wheel and broke the slim-image build.
+# Voice paths in code are lazily guarded; with VOICE_ENABLED=false (default),
+# the app starts cleanly. With voice enabled, missing imports log and
+# the feature gracefully degrades. To re-enable voice in a build, install
+# the `voice` extra: `pip install .[voice]` — and add an extras step here.
 
 # Build the fable-mcp wheel so it can be served for download
 COPY fable-mcp/ fable-mcp/