feat: implement pbUpsert helper for streamlined database operations and update related functions

src/lib/testService.js

@@ -1,5 +1,5 @@
 import * as db from './db';
-import { callLLM } from './llm';
+import { callLLM, cachedSystem } from './llm';
 import { EMIT_QUIZ_QUESTIONS_TOOL } from './llmTools';
 import { getCurriculumTopic, getQuarterForWeek } from './curriculumService';
 import { shuffle, sample } from './random';
@@ -25,8 +25,6 @@ const BANNED_OPTION_PATTERNS = [
   /both a and d/i,
 ];
 
-const cachedSystem = (text) => [{ type: 'text', text, cache_control: { type: 'ephemeral' } }];
-
 function normalizeQuestionText(text) {
   return String(text || '')
     .toLowerCase()