refactor: extract shared validation and reduce duplication

- Extract tool_types validation to shared module (validate_compose_yaml, check_port_exposed, validate_required_variables)
- Extract _get_user and _get_owned_project to auth/dependencies.py
- Create useAsyncData hook and apply to 6 pages
- Create extractErrorMessage utility
- TypeScript and build pass

apps/api/src/auth/dependencies.py

@@ -47,3 +47,39 @@ async def get_current_user(
     if user is None:
         raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="user not found")
     return user
+
+
+async def _get_user(session: AsyncSession, user_id: uuid.UUID) -> User:
+    """Fetch a user by ID or raise 401 if not found."""
+    user = await session.get(User, user_id)
+    if user is None:
+        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="user not found")
+    return user
+
+
+async def _get_owned_project(
+    project_id: uuid.UUID,
+    user_id: uuid.UUID,
+    session: AsyncSession,
+) -> "Project":
+    """Fetch a project and verify ownership.
+
+    Args:
+        project_id: UUID of the project.
+        user_id: ID of the authenticated user.
+        session: Database session.
+
+    Returns:
+        The project if found and owned by the user.
+
+    Raises:
+        HTTPException: 404 if project not found, 403 if user is not the owner.
+    """
+    from src.models.project import Project
+
+    project = await session.get(Project, project_id)
+    if project is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="project not found")
+    if project.owner_id != user_id:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="not project owner")
+    return project