Dockerize backend, frontend, and database into separate containers

- backend/Dockerfile: multi-stage Python build (builder + slim runtime)
- frontend/Dockerfile: multi-stage Node build + nginx:alpine serving
- frontend/nginx.conf: SPA routing + /api/ reverse proxy to backend
- docker-compose.yml: production compose with health checks and proper dependency ordering
- docker-compose.dev.yml: dev overrides with hot reload via volume mounts

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

docker-compose.yml

@@ -1,35 +1,46 @@
 services:
+
+  # ── Database ────────────────────────────────────────────────────────────────
   db:
-    image: postgres:16
+    image: postgres:16-alpine
+    restart: unless-stopped
     environment:
-      POSTGRES_USER: postgres
-      POSTGRES_PASSWORD: password
-      POSTGRES_DB: destroying_sap
+      POSTGRES_USER: ${POSTGRES_USER:-postgres}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-password}
+      POSTGRES_DB: ${POSTGRES_DB:-destroying_sap}
     ports:
       - "5432:5432"
     volumes:
       - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-postgres}"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
 
+  # ── Backend (management) ────────────────────────────────────────────────────
   backend:
-    build: ./backend
-    command: uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload
-    volumes:
-      - ./backend:/app
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    env_file: ./backend/.env
+    environment:
+      DATABASE_URL: postgresql+asyncpg://${POSTGRES_USER:-postgres}:${POSTGRES_PASSWORD:-password}@db:5432/${POSTGRES_DB:-destroying_sap}
     ports:
       - "8000:8000"
-    environment:
-      DATABASE_URL: postgresql+asyncpg://postgres:password@db:5432/destroying_sap
     depends_on:
-      - db
+      db:
+        condition: service_healthy
 
+  # ── Frontend (UI) ────────────────────────────────────────────────────────────
   frontend:
-    build: ./frontend
-    command: npm run dev -- --host
-    volumes:
-      - ./frontend:/app
-      - /app/node_modules
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile
+    restart: unless-stopped
     ports:
-      - "5173:5173"
+      - "80:80"
     depends_on:
       - backend