Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/app/schemas/__init__.py

@@ -0,0 +1,11 @@
+from .user import UserCreate, UserUpdate, UserResponse, UserLogin
+from .token import Token, TokenPayload
+from .tree import TreeCreate, TreeUpdate, TreeResponse, TreeListResponse
+from .session import SessionCreate, SessionUpdate, SessionResponse, SessionExport, DecisionRecord
+
+__all__ = [
+    "UserCreate", "UserUpdate", "UserResponse", "UserLogin",
+    "Token", "TokenPayload",
+    "TreeCreate", "TreeUpdate", "TreeResponse", "TreeListResponse",
+    "SessionCreate", "SessionUpdate", "SessionResponse", "SessionExport", "DecisionRecord"
+]