feat: implement audit trail module

- Backend (FastAPI):
  - AuditLog and AuditAlert models with Alembic migration
  - AuditService with SHA-256 checksum for log integrity
  - AuditMiddleware for request metadata extraction (IP, user_agent)
  - Integrated audit logging into Task, Project, Blocker APIs
  - Query API with filtering, pagination, CSV export
  - Integrity verification endpoint
  - Sensitive operation alerts with acknowledgement

- Frontend (React + Vite):
  - Admin AuditPage with filters and export
  - ResourceHistory component for change tracking
  - Audit service for API calls

- Testing:
  - 15 tests covering service and API endpoints

- OpenSpec:
  - add-audit-trail change archived

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

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

frontend/src/App.tsx

@@ -5,6 +5,7 @@ import Dashboard from './pages/Dashboard'
 import Spaces from './pages/Spaces'
 import Projects from './pages/Projects'
 import Tasks from './pages/Tasks'
+import AuditPage from './pages/AuditPage'
 import ProtectedRoute from './components/ProtectedRoute'
 import Layout from './components/Layout'
 
@@ -61,6 +62,16 @@ function App() {
           </ProtectedRoute>
         }
       />
+      <Route
+        path="/audit"
+        element={
+          <ProtectedRoute>
+            <Layout>
+              <AuditPage />
+            </Layout>
+          </ProtectedRoute>
+        }
+      />
     </Routes>
   )
 }