feat: add AI auto-fix UI — types, API client, ValidationSummary button, review modal, and TreeEditorPage wiring

- New ai-fix.ts types for request/response
- fixTree() method on treesApi
- "Fix with AI" button in ValidationSummary (shows for fixable errors)
- AIFixReviewModal with per-fix apply/skip and apply-all
- TreeEditorPage orchestrates the fix flow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/api/trees.ts

@@ -1,5 +1,5 @@
 import apiClient from './client'
-import type { Tree, TreeListItem, TreeCreate, TreeUpdate, TreeFilters, TreeShareCreate, TreeShare, TreeVisibilityUpdate, TreeValidationResponse } from '@/types'
+import type { Tree, TreeListItem, TreeCreate, TreeUpdate, TreeFilters, TreeShareCreate, TreeShare, TreeVisibilityUpdate, TreeValidationResponse, AIFixTreeRequest, AIFixTreeResponse } from '@/types'
 
 export const treesApi = {
   async list(params?: TreeFilters): Promise<TreeListItem[]> {
@@ -65,6 +65,12 @@ export const treesApi = {
     const response = await apiClient.post<TreeValidationResponse>(`/trees/${id}/can-publish`)
     return response.data
   },
+
+  // AI auto-fix
+  async fixTree(request: AIFixTreeRequest): Promise<AIFixTreeResponse> {
+    const response = await apiClient.post<AIFixTreeResponse>('/ai/fix-tree', request)
+    return response.data
+  },
 }
 
 export default treesApi