feat: complete workspace-first-ui cleanup and tests

- Delete dead repo-workspace code: RepoWorkspacePage, useRepoWorkspace,
  WorkspaceLayout, FileBrowser, old git components (git-toolbar, file-editor,
  commit-panel), and repo-workspace.css.
- Fix stale backend test imports for moved models/services.
- Add GitOperations unit tests.
- Add integration tests for workspace files, git, and instances endpoints.
- Add frontend tests for WorkspaceDetailPage and ProjectCard.
- Update OpenSpec workspace-first-ui tasks and mark change completed.
- Regenerate project maps.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (87 passed),
python3 -m py_compile on changed backend files, pytest backend workspace tests.

apps/api/tests/unit/test_file_service.py

@@ -5,8 +5,8 @@ import tempfile
 
 import pytest
 
-from src.models.workspace import Workspace
-from src.services.file_service import FileService
+from src.models import Workspace
+from src.services.shared.file_service import FileService
 
 
 @pytest.fixture