[Spec Kit] Implementation progress

Implements all 88 tasks for the Reaction Image Board (specs/001-reaction-image-board):

- docker-compose.yml: postgres, minio, minio-init, api, ui services with healthchecks
- api/: FastAPI app with SQLAlchemy 2.x async, Alembic migrations, S3/MinIO storage,
  full integration + unit test suite (pytest + pytest-asyncio)
- ui/: Angular 19 standalone app (Library, Upload, Detail, NotFound components)
- .env.example: all required environment variables
- .gitignore: Python, Node, Docker, IDE, .env patterns

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

api/app/database.py

@@ -0,0 +1,26 @@
+from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import get_settings
+
+_engine = None
+_session_factory = None
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_engine():
+    global _engine
+    if _engine is None:
+        settings = get_settings()
+        _engine = create_async_engine(settings.database_url, echo=False)
+    return _engine
+
+
+def get_session_factory():
+    global _session_factory
+    if _session_factory is None:
+        _session_factory = async_sessionmaker(get_engine(), expire_on_commit=False)
+    return _session_factory