Wire the app, worker, and cleanup entry points onto Prisma Client

Task 4 rewrote src/db.js and src/jobs/jobRepository.js to use Prisma
instead of the hand-rolled mariadb pool. This updates every remaining
call site (app.js, server.js, worker.js, cleanup.js) and the 5 test
files that still referenced getPool/closePool/pool.query, so the app
and full test suite compile and run against Prisma Client.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/server.js

@@ -1,13 +1,13 @@
 import { loadConfig } from './config.js';
-import { getPool } from './db.js';
+import { getPrismaClient } from './db.js';
 import { ensureStorageDirs } from './storage.js';
 import { createApp } from './app.js';
 
 async function main() {
   const config = loadConfig();
   await ensureStorageDirs(config);
-  const pool = getPool(config);
-  const app = createApp(config, pool);
+  const prisma = getPrismaClient(config);
+  const app = createApp(config, prisma);
 
   app.listen(config.port, () => {
     console.log(`File converter API listening on port ${config.port}`);