Rewrite from Go + vanilla JS to Python (FastAPI) + React (TypeScript)

- Backend: Python 3.12 with FastAPI, SQLAlchemy, boto3
- Frontend: React 18 with TypeScript, Vite build tooling
- Updated Dockerfile for multi-stage Node + Python build
- Updated CI pipeline for Python backend
- Removed old Go code (cmd/, internal/, go.mod, go.sum)
- Updated README with new tech stack documentation

backend/app/database.py

@@ -0,0 +1,25 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, Session
+from typing import Generator
+
+from .config import get_settings
+from .models import Base
+
+settings = get_settings()
+
+engine = create_engine(settings.database_url, pool_pre_ping=True)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def init_db():
+    """Create all tables"""
+    Base.metadata.create_all(bind=engine)
+
+
+def get_db() -> Generator[Session, None, None]:
+    """Dependency for getting database sessions"""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()