feat(matrix-bridge-dagi): scaffold service with health, metrics and config (PR-M1.0)

New service: services/matrix-bridge-dagi/
- app/config.py: BridgeConfig dataclass, load_config() with full env validation
  (MATRIX_HOMESERVER_URL, MATRIX_ACCESS_TOKEN, MATRIX_USER_ID, SOFIIA_ROOM_ID,
   DAGI_GATEWAY_URL, SOFIIA_CONSOLE_URL, SOFIIA_INTERNAL_TOKEN, rate limits)
- app/main.py: FastAPI app with lifespan, GET /health, GET /metrics (prometheus)
  health returns: ok, node_id, homeserver, bridge_user, sofiia_room_id,
  allowed_agents, gateway, uptime_s; graceful error state when config missing
- requirements.txt: fastapi, uvicorn, httpx, prometheus-client, pyyaml
- Dockerfile: python:3.11-slim, port 7030, BUILD_SHA/BUILD_TIME args

docker-compose.matrix-bridge-node1.yml:
- standalone override file (node1 network, port 127.0.0.1:7030)
- all env vars wired: MATRIX_*, SOFIIA_ROOM_ID, DAGI_GATEWAY_URL,
  SOFIIA_CONSOLE_URL, SOFIIA_INTERNAL_TOKEN, rate limit policy
- healthcheck, restart: unless-stopped

DoD: config validates, health/metrics respond, imports clean
Made-with: Cursor

services/matrix-bridge-dagi/Dockerfile

@@ -0,0 +1,17 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY app/ ./app/
+
+ARG BUILD_SHA=dev
+ARG BUILD_TIME=local
+ENV BUILD_SHA=${BUILD_SHA}
+ENV BUILD_TIME=${BUILD_TIME}
+
+ENV PYTHONUNBUFFERED=1
+ENV PORT=7030
+EXPOSE 7030
+
+CMD ["sh", "-c", "uvicorn app.main:app --host 0.0.0.0 --port ${PORT:-7030}"]