chore: update compose.demo.yml for Vue/FastAPI architecture

Replace the legacy Streamlit `app` service with a FastAPI `api` service
running dev_api:app on port 8601. The Vue SPA (nginx) proxies /api/ →
api:8601 internally so no host port is needed on the api container.

Move web service from port 8507 → 8504 to match the documented demo URL
(demo.circuitforge.tech/peregrine via Caddy → host:8504).

compose.demo.yml

@@ -15,10 +15,10 @@
 
 services:
 
-  app:
+  api:
     build: .
-    ports:
-      - "8504:8501"
+    command: >
+      bash -c "uvicorn dev_api:app --host 0.0.0.0 --port 8601"
     volumes:
       - ./demo/config:/app/config
       - ./demo:/app/demo:ro   # seed.sql lives here; read-only
@@ -30,7 +30,6 @@ services:
       - STAGING_DB=/app/data/staging.db
       - DEMO_SEED_FILE=/app/demo/seed.sql
       - DOCS_DIR=/tmp/demo-docs
-      - STREAMLIT_SERVER_BASE_URL_PATH=peregrine
       - PYTHONUNBUFFERED=1
       - PYTHONLOGGING=WARNING
       # No API keys — inference is blocked by DEMO_MODE before any key is needed
@@ -40,6 +39,7 @@ services:
     extra_hosts:
       - "host.docker.internal:host-gateway"
     restart: unless-stopped
+    # No host port — nginx proxies /api/ → api:8601 internally
 
   web:
     build:
@@ -48,7 +48,9 @@ services:
       args:
         VITE_BASE_PATH: /peregrine/
     ports:
-      - "8507:80"
+      - "8504:80"   # demo.circuitforge.tech/peregrine* → host:8504
+    depends_on:
+      - api
     restart: unless-stopped
 
   searxng: