FE-CAL-001/002/003: Add Calendar page with daily slot view and plans tab

- New CalendarPage with daily view (date navigation, slot list) and plans tab
- Route /calendar added in App.tsx
- Sidebar entry added after Proposals
- Daily view: shows time slots with type, status, priority, duration, event data
- Distinguishes real vs virtual (plan) slots visually
- Plans tab: shows schedule plan rules with schedule parameters

src/App.tsx

@@ -17,6 +17,7 @@ import MonitorPage from '@/pages/MonitorPage'
 import ProposalsPage from '@/pages/ProposalsPage'
 import ProposalDetailPage from '@/pages/ProposalDetailPage'
 import UsersPage from '@/pages/UsersPage'
+import CalendarPage from '@/pages/CalendarPage'
 import SupportDetailPage from '@/pages/SupportDetailPage'
 import MeetingDetailPage from '@/pages/MeetingDetailPage'
 import axios from 'axios'
@@ -118,6 +119,7 @@ export default function App() {
             <Route path="/milestones/:id" element={<MilestoneDetailPage />} />
             <Route path="/proposals" element={<ProposalsPage />} />
             <Route path="/proposals/:id" element={<ProposalDetailPage />} />
+            <Route path="/calendar" element={<CalendarPage />} />
             {/* Legacy routes for backward compatibility */}
             <Route path="/proposes" element={<ProposalsPage />} />
             <Route path="/proposes/:id" element={<ProposalDetailPage />} />