Enable GPU: LLM + Whisper on the RTX 5050, pick qwen3:8b

GPU acceleration is now on by default and verified end-to-end on the
Blackwell RTX 5050 (sm_120):

- Ollama offloads 100% to GPU (log: library=CUDA compute=12.0,
  BLACKWELL_NATIVE_FP4=1). compose passes GPU via CDI
  (devices: nvidia.com/gpu=all) to both ollama and javis.
- Whisper STT on GPU: faster-whisper>=1.1.0 + nvidia-cublas/cudnn cu12,
  LD_LIBRARY_PATH baked into the image. Verified float16 transcribe on
  sm_120; bridge auto-falls back to CPU when no GPU is present.
- Model: default chat model -> qwen3:8b (best 8GB-VRAM tool-calling,
  ~5GB Q4). Embed stays nomic-embed-text.
- README documents the host one-time setup (nvidia-container-toolkit +
  `nvidia-ctk cdi generate`) and GPU on/off.

Verified: image builds; GPU visible in both containers via compose;
ollama ps = 100% GPU; faster-whisper cuda OK + CPU fallback OK;
bridge /health 200.

Dockerfile

@@ -8,7 +8,10 @@ FROM ubuntu:24.04
 ENV DEBIAN_FRONTEND=noninteractive \
     LANG=C.UTF-8 \
     DISPLAY=:1 \
-    PATH=/opt/venv/bin:/root/.bun/bin:/usr/local/bin:/usr/bin:/bin
+    PATH=/opt/venv/bin:/root/.bun/bin:/usr/local/bin:/usr/bin:/bin \
+    NVIDIA_VISIBLE_DEVICES=all \
+    NVIDIA_DRIVER_CAPABILITIES=compute,utility \
+    LD_LIBRARY_PATH=/opt/venv/lib/python3.12/site-packages/nvidia/cublas/lib:/opt/venv/lib/python3.12/site-packages/nvidia/cudnn/lib
 
 # --- System packages: desktop, VNC, Chrome deps, ffmpeg, python, ocr ---
 RUN apt-get update && apt-get install -y --no-install-recommends \