feat(m11): calendar + milestones with progress calc, tests, e2e

- CalendarRepository (event CRUD, range query, soft-delete, project isolation)
  + MilestoneRepository (CRUD, findToDosByMilestone) + ScheduleService
  (aggregated getCalendarEvents = custom events+milestones+todos in range,
  milestone CRUD, milestone_updated activity, progress auto-calc 0-100)
- APIs: calendar events GET/POST/PATCH/DELETE, milestones GET/POST/PATCH +
  progress
- Screens: calendar list view + CalendarEventForm, milestones list with
  progress bars + MilestoneForm, ProjectNav links
- Unit tests (CalendarRepository, MilestoneRepository, ScheduleService incl.
  progress calc 0/33/100) + e2e calendar

components/layout/ProjectNav.tsx

@@ -5,6 +5,8 @@ const NAV_ITEMS = [
   { href: '/chat', label: 'チャット' },
   { href: '/todos', label: 'ToDo' },
   { href: '/files', label: 'ファイル' },
+  { href: '/calendar', label: 'カレンダー' },
+  { href: '/milestones', label: 'マイルストーン' },
   { href: '/members', label: 'メンバー' },
   { href: '/activity', label: 'アクティビティ' },
   { href: '/settings', label: '設定' },
@@ -26,6 +28,8 @@ export function ProjectNav({
     | 'chat'
     | 'todos'
     | 'files'
+    | 'calendar'
+    | 'milestones'
     | 'members'
     | 'activity'
     | 'settings';
@@ -37,6 +41,8 @@ export function ProjectNav({
     chat: active === 'chat',
     todos: active === 'todos',
     files: active === 'files',
+    calendar: active === 'calendar',
+    milestones: active === 'milestones',
     members: active === 'members',
     activity: active === 'activity',
     settings: active === 'settings',