feat(dwg): DWG→DXF via sidecar microservice (libredwg)

Add dedicated dwg2dxf container (Debian slim + libredwg-tools + Flask)
instead of modifying the Alpine base image. The ArchiTools API route
proxies to the sidecar over Docker internal network.

- dwg2dxf-api/: Dockerfile + Flask app (POST /convert, GET /health)
- docker-compose.yml: dwg2dxf service, healthcheck, depends_on
- route.ts: rewritten from local exec to HTTP proxy
- .dockerignore: exclude sidecar from main build context

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -44,8 +44,25 @@ services:
       # eTerra ANCPI (parcel-sync module)
       - ETERRA_USERNAME=${ETERRA_USERNAME:-}
       - ETERRA_PASSWORD=${ETERRA_PASSWORD:-}
+      # DWG-to-DXF sidecar
+      - DWG2DXF_URL=http://dwg2dxf:5001
+    depends_on:
+      dwg2dxf:
+        condition: service_healthy
     volumes:
       # SMB share for ManicTime Tags.txt (mount on host: //time/tags → /mnt/manictime)
       - /mnt/manictime:/mnt/manictime
     labels:
       - "com.centurylinklabs.watchtower.enable=true"
+
+  dwg2dxf:
+    build:
+      context: ./dwg2dxf-api
+    container_name: dwg2dxf
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python3", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:5001/health')"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s