v2.0: dual deployment — pip install (SQLite) + Docker (PostgreSQL)

Architecture:
- Moved backend/app/ to diligence/ Python package
- Dialect-agnostic models (Uuid + JSON, no PostgreSQL imports)
- Auto-detect database: empty DATABASE_URL → SQLite at ~/.diligence/data.db
- Cross-dialect migrations (inspector-based, no raw PostgreSQL DDL)
- FastAPI serves pre-built React frontend for pip path
- CLI entry point: diligence [--port] [--no-browser] [--data-dir]
- pyproject.toml with optional deps: [postgres], [mcp], [dev]
- Docker path unchanged: docker compose up -d

pip install path: pip install . && diligence
Docker path: ./setup.sh && docker compose up -d

docker-compose.yml

@@ -15,10 +15,13 @@ services:
       start_period: 10s
 
   backend:
-    build: ./backend
+    build:
+      context: .
+      dockerfile: backend/Dockerfile
     restart: unless-stopped
     env_file: .env
     environment:
+      - DATABASE_URL=postgresql+asyncpg://fitness@fitness-db:5432/fitness_rewards
       - BASE_URL=${BASE_URL:-http://localhost}
       - API_TOKEN=${API_TOKEN:-}
     depends_on: