feat: maintenance flows frontend foundation - types, API clients, sidebar, library filter

- Add maintenance.ts types: TargetEntry, TargetList, MaintenanceSchedule, BatchLaunch
- Add targetListsApi and maintenanceSchedulesApi/batchLaunchApi clients
- Extend TreeType union with 'maintenance' in tree.ts
- Update getTreeNavigatePath/getTreeEditorPath in routing.ts for maintenance
- Sidebar: track maintenance count and add Maintenance sub-nav item
- TreeLibraryPage: add maintenance to typeFilter state, URL sync, and tab buttons
- TreeGridView, TreeListView, TreeTableView: add amber Wrench maintenance badge

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

frontend/src/api/maintenanceSchedules.ts

@@ -0,0 +1,24 @@
+import { apiClient } from './client'
+import type {
+  MaintenanceSchedule,
+  MaintenanceScheduleCreate,
+  MaintenanceScheduleUpdate,
+  BatchLaunchRequest,
+  BatchLaunchResponse,
+} from '@/types'
+
+export const maintenanceSchedulesApi = {
+  getForTree: (treeId: string): Promise<MaintenanceSchedule> =>
+    apiClient.get(`/maintenance-schedules/tree/${treeId}`).then(r => r.data),
+
+  create: (data: MaintenanceScheduleCreate): Promise<MaintenanceSchedule> =>
+    apiClient.post('/maintenance-schedules', data).then(r => r.data),
+
+  update: (id: string, data: MaintenanceScheduleUpdate): Promise<MaintenanceSchedule> =>
+    apiClient.patch(`/maintenance-schedules/${id}`, data).then(r => r.data),
+}
+
+export const batchLaunchApi = {
+  launch: (data: BatchLaunchRequest): Promise<BatchLaunchResponse> =>
+    apiClient.post('/sessions/batch', data).then(r => r.data),
+}