feat: support external repositories for git mounts

- Make project_id nullable in git_repositories table (migration)
- Allow external repos not tied to any project
- Update validation to allow user-owned external repos in git mounts
- Add /projects/repositories endpoint to list all user repos
- Update frontend to fetch all user repos for git mount selector
- TypeScript and build pass

apps/api/src/api/config_profiles.py

@@ -275,8 +275,10 @@ async def _validate_git_mounts(
     
     Repositories must:
     1. Exist
-    2. Belong to the user
-    3. If project_id is specified, belong to that project
+    2. Belong to the user (external repos with no project are allowed)
+    3. If project_id is specified, repos can be either:
+       - External repos (project_id is null) belonging to the user
+       - Project repos belonging to that project
     """
     for mount in git_mounts:
         repo_id = mount.get("repo_id")
@@ -307,6 +309,11 @@ async def _validate_git_mounts(
                 detail=f"Not authorized to access repository: {repo_id}",
             )
         
+        # External repos (no project) are always allowed for git mounts
+        if repo.project_id is None:
+            continue
+        
+        # Project repos are allowed if they belong to the profile's project
         if project_id is not None and repo.project_id != project_id:
             raise HTTPException(
                 status_code=status.HTTP_400_BAD_REQUEST,

apps/api/src/api/git_repositories.py

@@ -262,6 +262,31 @@ async def list_repositories(
     return list(result.scalars().all())
 
 
+@router.get(
+    "/repositories",
+    response_model=list[GitRepositoryResponse],
+    summary="List all user repositories",
+    description="List all git repositories owned by the user, including external repositories not tied to any project.",
+)
+async def list_user_repositories(
+    user_id: uuid.UUID = Depends(get_current_user_id),
+    session: AsyncSession = Depends(get_db_session),
+) -> list[GitRepository]:
+    """List all repositories owned by the user.
+
+    Args:
+        user_id: ID of the authenticated user.
+        session: Database session.
+
+    Returns:
+        List of all repositories owned by the user.
+    """
+    result = await session.execute(
+        select(GitRepository).where(GitRepository.owner_id == user_id)
+    )
+    return list(result.scalars().all())
+
+
 @router.delete(
     "/{project_id}/repositories/{repo_id}",
     status_code=status.HTTP_204_NO_CONTENT,

apps/api/src/models/git_repository.py

@@ -19,7 +19,7 @@ class GitRepository(UUIDPrimaryKeyMixin, TimestampMixin, Base):
 
     name: Mapped[str] = mapped_column(String(255))
     path: Mapped[str] = mapped_column(String(1024))
-    project_id: Mapped[uuid.UUID] = mapped_column(UUID(), ForeignKey("projects.id"), nullable=False)
+    project_id: Mapped[uuid.UUID | None] = mapped_column(UUID(), ForeignKey("projects.id"), nullable=True)
     owner_id: Mapped[uuid.UUID] = mapped_column(UUID(), ForeignKey("users.id"), nullable=False)
     is_mirror: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
     remote_url: Mapped[str | None] = mapped_column(String(1024), nullable=True)