fix(frontend): 修复合并审阅发现的构建与契约问题

恢复 Vue TypeScript 生产构建，补齐可运行页面壳子，并修复文件树与 SSE 状态问题。

按 FastAPI Wire Contract 统一 Service DTO 映射，同时补充前端开发说明和问题修复复盘。

frontend/src/services/searchService.ts

@@ -1,15 +1,45 @@
 import apiClient from './apiClient'
-import type { SearchRequest, SearchResult } from '@/contracts'
+import type { ApiSearchResult, PageMeta, SearchRequest, SearchResult } from '@/contracts'
 
 export async function search(request: SearchRequest): Promise<{
   results: SearchResult[]
   total: number
   mode: SearchRequest['mode']
 }> {
-  return apiClient.post('/api/search', request)
+  const response = await apiClient.post<{
+    query: string
+    mode: 'fts' | 'vector' | 'hybrid'
+    items: ApiSearchResult[]
+    page: PageMeta
+  }>('/api/search', {
+    query: request.query,
+    mode: request.mode ?? 'hybrid',
+    folders: request.folder ? [request.folder] : [],
+    note_ids: request.note_id ? [request.note_id] : [],
+    tags: request.tag ? [request.tag] : [],
+    limit: request.limit ?? 20,
+    offset: request.offset ?? 0,
+  })
+  return {
+    results: response.items.map((item) => ({
+      block_id: item.block_id,
+      note_id: item.note_id,
+      note_title: item.title,
+      file_path: item.file_path,
+      heading_path: item.heading_path.join(' / '),
+      snippet: item.snippet ?? '',
+      score: item.score,
+      match_type: response.mode,
+    })),
+    total: response.page.total,
+    mode: response.mode,
+  }
 }
 
-export async function searchMock(query: string, mode = 'hybrid' as const): Promise<{
+export async function searchMock(
+  query: string,
+  mode: 'fts' | 'vector' | 'hybrid' = 'hybrid'
+): Promise<{
   results: SearchResult[]
   total: number
   mode: 'fts' | 'vector' | 'hybrid'