Mode-3: Question bank page + custom-paper assembly UI

New /exam-marker/bank page: browse leaf questions across your papers, filter by
spec point (the spec-planning surface) and subject via facet chips, select
questions into a basket, and "Create paper" → POST /custom-papers → opens the new
template in setup. Dashboard gets a "Question bank" entry point.

examRepository.getBank + createCustomPaper; BankQuestion/BankResponse/custom-paper
types. tsc clean. Pairs with the mode-3 API endpoints (already merged).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/services/exam/examRepository.ts

@@ -13,9 +13,12 @@ import { supabase } from '../../supabaseClient';
 import type {
   AutoMapJobStatus,
   AutoMapResponse,
+  BankResponse,
   BatchQueueResponse,
   BatchResultsResponse,
   CreateBatchPayload,
+  CreateCustomPaperPayload,
+  CreateCustomPaperResult,
   CreateTemplatePayload,
   ExamBoundary,
   ExamQuestion,
@@ -300,6 +303,21 @@ export const examRepository = {
     return res.data;
   },
 
+  async getBank(params: { specRef?: string; subject?: string } = {}): Promise<BankResponse> {
+    const headers = await authHeaders();
+    const res = await axios.get<BankResponse>(`${EXAM_BASE}/bank`, {
+      headers,
+      params: { spec_ref: params.specRef, subject: params.subject },
+    });
+    return res.data;
+  },
+
+  async createCustomPaper(payload: CreateCustomPaperPayload): Promise<CreateCustomPaperResult> {
+    const headers = await authHeaders();
+    const res = await axios.post<CreateCustomPaperResult>(`${EXAM_BASE}/custom-papers`, payload, { headers });
+    return res.data;
+  },
+
   async uploadScan(
     batchId: string,
     file: File,