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/api/deps.py

@@ -0,0 +1,82 @@
+from typing import Annotated
+from uuid import UUID
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy import select
+
+from app.core.database import get_db
+from app.core.security import decode_token
+from app.models.user import User
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")
+
+
+async def get_current_user(
+    db: Annotated[AsyncSession, Depends(get_db)],
+    token: Annotated[str, Depends(oauth2_scheme)]
+) -> User:
+    """Get current authenticated user from JWT token."""
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+
+    payload = decode_token(token)
+    if payload is None:
+        raise credentials_exception
+
+    token_type = payload.get("type")
+    if token_type != "access":
+        raise credentials_exception
+
+    user_id: str = payload.get("sub")
+    if user_id is None:
+        raise credentials_exception
+
+    try:
+        user_uuid = UUID(user_id)
+    except ValueError:
+        raise credentials_exception
+
+    result = await db.execute(select(User).where(User.id == user_uuid))
+    user = result.scalar_one_or_none()
+
+    if user is None:
+        raise credentials_exception
+
+    return user
+
+
+async def get_current_active_user(
+    current_user: Annotated[User, Depends(get_current_user)]
+) -> User:
+    """Ensure user is active (not disabled)."""
+    # For now, all users are considered active
+    # Add logic here if you add an is_active field to User
+    return current_user
+
+
+async def require_admin(
+    current_user: Annotated[User, Depends(get_current_active_user)]
+) -> User:
+    """Require admin role."""
+    if current_user.role != "admin":
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Admin access required"
+        )
+    return current_user
+
+
+async def require_engineer_or_admin(
+    current_user: Annotated[User, Depends(get_current_active_user)]
+) -> User:
+    """Require engineer or admin role."""
+    if current_user.role not in ("admin", "engineer"):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Engineer or admin access required"
+        )
+    return current_user