feat: implement user authentication module

- Backend (FastAPI):
  - External API authentication (pj-auth-api.vercel.app)
  - JWT token validation with Redis session storage
  - RBAC with department isolation
  - User, Role, Department models with pjctrl_ prefix
  - Alembic migrations with project-specific version table
  - Complete test coverage (13 tests)

- Frontend (React + Vite):
  - AuthContext for state management
  - Login page with error handling
  - Protected route component
  - Dashboard with user info display

- OpenSpec:
  - 7 capability specs defined
  - add-user-auth change archived

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/commands/openspec/apply.md

@@ -0,0 +1,23 @@
+---
+name: OpenSpec: Apply
+description: Implement an approved OpenSpec change and keep tasks in sync.
+category: OpenSpec
+tags: [openspec, apply]
+---
+<!-- OPENSPEC:START -->
+**Guardrails**
+- Favor straightforward, minimal implementations first and add complexity only when it is requested or clearly required.
+- Keep changes tightly scoped to the requested outcome.
+- Refer to `openspec/AGENTS.md` (located inside the `openspec/` directory—run `ls openspec` or `openspec update` if you don't see it) if you need additional OpenSpec conventions or clarifications.
+
+**Steps**
+Track these steps as TODOs and complete them one by one.
+1. Read `changes/<id>/proposal.md`, `design.md` (if present), and `tasks.md` to confirm scope and acceptance criteria.
+2. Work through tasks sequentially, keeping edits minimal and focused on the requested change.
+3. Confirm completion before updating statuses—make sure every item in `tasks.md` is finished.
+4. Update the checklist after all work is done so each task is marked `- [x]` and reflects reality.
+5. Reference `openspec list` or `openspec show <item>` when additional context is required.
+
+**Reference**
+- Use `openspec show <id> --json --deltas-only` if you need additional context from the proposal while implementing.
+<!-- OPENSPEC:END -->