fix(backend): Deezer proxy route crashed the whole server on Express 5

`app.get('/api/deezer/*', …)` — a bare "*" — throws "Missing parameter name" in
Express 5's path-to-regexp at startup, so the server never came up and EVERY endpoint
(abs-proxy, romaji-overrides, deezer, …) failed with a CORS/ERR_FAILED in the browser.
Use a RegExp route instead, which registers cleanly on both Express 4 and 5. Verified
against express 5.2.1: bare "*" crashes, the regex is OK.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/novasonic-server.js

@@ -327,7 +327,9 @@ app.get('/api/itunes/:endpoint', (req, res) => {
 // Deezer API proxy — the search source (Apple's /search returns 403 from server IPs). Deezer is
 // free, needs no key, and returns explicit versions + artist images + track durations. Covers
 // /search, /search/album, /search/artist, /album/{id}, /album/{id}/tracks, /artist/{id}/albums, …
-app.get('/api/deezer/*', (req, res) => {
+// Regex route (not '/api/deezer/*') — a bare "*" is an invalid path pattern in Express 5 and
+// crashes the server at startup, taking every endpoint down with it.
+app.get(/^\/api\/deezer\/(.+)/, (req, res) => {
   const sub = String(req.params[0] || '').replace(/[^a-zA-Z0-9/_-]/g, '');
   const qs  = new URLSearchParams(req.query).toString();
   const target = `https://api.deezer.com/${sub}${qs ? '?' + qs : ''}`;