ci: run svelte-check, which was already a dependency with no script

svelte-check sits in devDependencies at ^4.7.3 and nothing in the repository
ever invoked it, so the type errors it reports had no path to a human. Point a
script at it and run it in the frontend job, and it is clean: 0 errors, 0
warnings.

It shares the one `npm ci` with the test step. A second install would have
doubled the slowest part of the job to learn exactly the same thing.

The lockfile is untouched, because scripts are not part of what it pins.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

userbot/panel/frontend/package.json

@@ -6,7 +6,8 @@
   "scripts": {
     "build": "vite build",
     "dev": "vite --host 0.0.0.0",
-    "test": "vitest run"
+    "test": "vitest run",
+    "check": "svelte-check --tsconfig ./tsconfig.json"
   },
   "dependencies": {
     "lucide-svelte": "^0.468.0",