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>

frontend/src/pages/Dashboard.tsx

@@ -0,0 +1,115 @@
+import { useAuth } from '../contexts/AuthContext'
+
+export default function Dashboard() {
+  const { user, logout } = useAuth()
+
+  const handleLogout = async () => {
+    await logout()
+  }
+
+  return (
+    <div style={styles.container}>
+      <header style={styles.header}>
+        <h1 style={styles.title}>Project Control</h1>
+        <div style={styles.userInfo}>
+          <span style={styles.userName}>{user?.name}</span>
+          {user?.is_system_admin && (
+            <span style={styles.badge}>Admin</span>
+          )}
+          <button onClick={handleLogout} style={styles.logoutButton}>
+            Logout
+          </button>
+        </div>
+      </header>
+
+      <main style={styles.main}>
+        <div style={styles.welcomeCard}>
+          <h2>Welcome, {user?.name}!</h2>
+          <p>Email: {user?.email}</p>
+          <p>Role: {user?.role || 'No role assigned'}</p>
+          {user?.is_system_admin && (
+            <p style={styles.adminNote}>
+              You have system administrator privileges.
+            </p>
+          )}
+        </div>
+
+        <div style={styles.infoCard}>
+          <h3>Getting Started</h3>
+          <p>
+            This is the Project Control system dashboard. Features will be
+            added as development progresses.
+          </p>
+        </div>
+      </main>
+    </div>
+  )
+}
+
+const styles: { [key: string]: React.CSSProperties } = {
+  container: {
+    minHeight: '100vh',
+    backgroundColor: '#f5f5f5',
+  },
+  header: {
+    display: 'flex',
+    justifyContent: 'space-between',
+    alignItems: 'center',
+    padding: '16px 24px',
+    backgroundColor: 'white',
+    boxShadow: '0 1px 3px rgba(0, 0, 0, 0.1)',
+  },
+  title: {
+    fontSize: '20px',
+    fontWeight: 600,
+    color: '#333',
+    margin: 0,
+  },
+  userInfo: {
+    display: 'flex',
+    alignItems: 'center',
+    gap: '12px',
+  },
+  userName: {
+    color: '#666',
+  },
+  badge: {
+    backgroundColor: '#0066cc',
+    color: 'white',
+    padding: '2px 8px',
+    borderRadius: '4px',
+    fontSize: '12px',
+    fontWeight: 500,
+  },
+  logoutButton: {
+    padding: '8px 16px',
+    backgroundColor: '#f5f5f5',
+    border: '1px solid #ddd',
+    borderRadius: '4px',
+    cursor: 'pointer',
+    fontSize: '14px',
+  },
+  main: {
+    padding: '24px',
+    maxWidth: '1200px',
+    margin: '0 auto',
+  },
+  welcomeCard: {
+    backgroundColor: 'white',
+    padding: '24px',
+    borderRadius: '8px',
+    boxShadow: '0 1px 3px rgba(0, 0, 0, 0.1)',
+    marginBottom: '24px',
+  },
+  adminNote: {
+    color: '#0066cc',
+    fontWeight: 500,
+    marginTop: '12px',
+  },
+  infoCard: {
+    backgroundColor: 'white',
+    padding: '24px',
+    borderRadius: '8px',
+    boxShadow: '0 1px 3px rgba(0, 0, 0, 0.1)',
+  },
+}