Initial commit: RealSense D435 API server

Drop-in replacement for the Nuwa-HP60C camera container, exposing RGB +
aligned depth + intrinsics via REST/WebSocket so the existing
pestello-pose-detector pipeline can consume frames without changes.

Key adaptations for D4xx on USB 2.0 (this robot has no USB 3 port exposed
externally — see STATUS.md):
- pyrealsense2 built from source; the librealsense v2.55.1 install rule
  doesn't ship the main .so, so we copy it from the build dir and add an
  __init__.py that re-exports the submodule.
- Color stream uses YUYV format on USB 2.x (BGR8/RGB8 time out on this
  bus); converted to BGR via cv2.cvtColor in capture().
- rs.align is skipped on USB 2 (incompatible with YUYV); color is
  cv2-resized to depth shape for approximate per-pixel alignment.
- Driver auto-detects usb_type_descriptor and falls back to the
  full-resolution BGR8 + rs.align pipeline when on USB 3.

Tested: /api/{health,status,discover,rgb,depth,depth/color,capture,
intrinsics} all return 200 with valid payloads at 640x480.

docker-compose.yml

@@ -0,0 +1,59 @@
+services:
+
+  # -- NATS Server ----------------------------
+  nats:
+    image: nats:latest
+    profiles: ["nats"]
+    ports:
+      - "4222:4222"
+      - "8222:8222"
+    command: >
+      --auth ${NATS_TOKEN:-realsense-dev-token}
+      --http_port 8222
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "nats-server", "--help"]
+      interval: 5s
+      timeout: 3s
+      retries: 3
+      start_period: 5s
+
+  # -- Backend --------------------------------
+  backend:
+    build:
+      context: .
+      dockerfile: Dockerfile
+      # network: host so that build-time apt/git/pip can reach the
+      # tinyproxy running on the host at localhost:8888.
+      network: host
+    privileged: true
+    ports:
+      - "${API_PORT:-8878}:8878"
+    devices:
+      - "/dev/bus/usb:/dev/bus/usb"
+    volumes:
+      - ./images:/app/images
+      - ./models:/app/models:ro
+    env_file: .env
+    depends_on:
+      nats:
+        condition: service_healthy
+        required: false
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python3", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8878/api/health')"]
+      interval: 10s
+      timeout: 5s
+      retries: 3
+
+  # -- Frontend React Dev (hot reload) --------
+  frontend-dev:
+    image: node:20-alpine
+    working_dir: /app
+    volumes:
+      - ./src/frontend/react:/app
+      - /app/node_modules
+    command: sh -c "npm ci && npm run dev -- --host 0.0.0.0"
+    ports:
+      - "5173:5173"
+    profiles: [dev]