step 1 complete: runnable FastAPI skeleton

- Full directory structure with all __init__.py stubs
- requirements.txt with all pinned dependencies
- app/config/settings.py (BaseSettings, env-based)
- app/main.py (CORS, lifespan, /api/v1/health)
- Dockerfile (multi-stage, Python 3.12-slim, non-root user)
- docker-compose.yml (app + postgres:16 with healthcheck)
- .env.example
- BACKEND_PLAN.md: mark step 1 done, add one-step-at-a-time rule

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

docker-compose.yml

@@ -0,0 +1,38 @@
+version: "3.9"
+
+services:
+  app:
+    build: .
+    ports:
+      - "8000:8000"
+    env_file:
+      - .env
+    environment:
+      DATABASE_URL: postgresql+asyncpg://postgres:postgres@db:5432/adiuva
+    depends_on:
+      db:
+        condition: service_healthy
+    restart: unless-stopped
+
+  db:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_DB: adiuva
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+    restart: unless-stopped
+
+  # Optional Redis for future rate-limit or caching needs
+  # redis:
+  #   image: redis:7-alpine
+  #   restart: unless-stopped
+
+volumes:
+  postgres_data: