feat: admin survey responses page with expandable detail and CSV export

- Backend: GET /admin/survey-responses (list with stats, invite join)
- Backend: GET /admin/survey-responses/export (CSV download)
- Frontend: SurveyResponsesPage with expandable row detail
- Two-column Q&A grid with typed answer rendering (chips, ranked lists, quote blocks)
- Stats cards (total responses, this week)
- CSV export button with blob download
- Sidebar nav + route wiring
- Also: updated Q14 from product domain ranking to diagnostic prioritization

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

frontend/src/api/admin.ts

@@ -32,6 +32,21 @@ export interface SurveyInviteResponse {
   survey_url: string
 }
 
+export interface SurveyResponseDetail {
+  id: string
+  respondent_name: string | null
+  responses: Record<string, string | string[]>
+  source: 'invite' | 'direct'
+  invite_name: string | null
+  created_at: string
+}
+
+export interface SurveyResponseListResponse {
+  responses: SurveyResponseDetail[]
+  total: number
+  this_week: number
+}
+
 export const adminApi = {
   // Dashboard
   getDashboardMetrics: () =>
@@ -158,6 +173,12 @@ export const adminApi = {
     api.get<SurveyInviteResponse[]>('/admin/survey-invites').then(r => r.data),
   createSurveyInvite: (data: { recipient_name: string; recipient_email?: string; send_email?: boolean }) =>
     api.post<SurveyInviteResponse>('/admin/survey-invites', data).then(r => r.data),
+
+  // Survey Responses
+  listSurveyResponses: () =>
+    api.get<SurveyResponseListResponse>('/admin/survey-responses').then(r => r.data),
+  exportSurveyResponsesCsv: () =>
+    api.get('/admin/survey-responses/export', { responseType: 'blob' }).then(r => r.data),
 }
 
 export default adminApi