chore: consolidate to single Docker container

Replace two-container setup (separate backend + nginx frontend) with a
single image that runs both via supervisord:

- New Dockerfile: Node stage builds React, Python+nginx stage is the runtime
- supervisord.conf: manages uvicorn (api_server.py) + nginx as sibling procs
- nginx.conf: proxy_pass updated to localhost:8000 (same container)
- docker-compose.yml: simplified to one service on port 80

Deploy:
  docker-compose up -d        # or
  docker build -t flight-radar . && docker run -p 80:80 flight-radar

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

flight-comparator/docker-compose.yml

@@ -1,54 +1,15 @@
 services:
-  # Backend API Server
-  backend:
-    build:
-      context: .
-      dockerfile: Dockerfile.backend
-    container_name: flight-radar-backend
-    restart: unless-stopped
-    ports:
-      - "8000:8000"
-    environment:
-      - PORT=8000
-      - DATABASE_PATH=/app/data/cache.db
-      - ALLOWED_ORIGINS=http://localhost,http://localhost:80,http://frontend
-    volumes:
-      - backend-data:/app/data
-      - ./cache.db:/app/cache.db:rw
-    networks:
-      - flight-radar-network
-    healthcheck:
-      test: ["CMD", "python", "-c", "import requests; requests.get('http://localhost:8000/health').raise_for_status()"]
-      interval: 30s
-      timeout: 3s
-      retries: 3
-      start_period: 10s
-
-  # Frontend UI
-  frontend:
-    build:
-      context: .
-      dockerfile: Dockerfile.frontend
-    container_name: flight-radar-frontend
+  app:
+    build: .
+    container_name: flight-radar
     restart: unless-stopped
     ports:
       - "80:80"
-    depends_on:
-      backend:
-        condition: service_healthy
-    networks:
-      - flight-radar-network
-    healthcheck:
-      test: ["CMD", "wget", "--quiet", "--tries=1", "--spider", "http://localhost/"]
-      interval: 30s
-      timeout: 3s
-      retries: 3
-      start_period: 5s
-
-networks:
-  flight-radar-network:
-    driver: bridge
+    environment:
+      - DATABASE_PATH=/app/data/cache.db
+    volumes:
+      - flight-radar-data:/app/data
 
 volumes:
-  backend-data:
+  flight-radar-data:
     driver: local