feat: comprehensive application audit and fixes

Audited codebase, fixed input validation, OAuth, error handling, type casts, and security hardening

Co-authored-by: Moheeb Zara <[email protected]>

app/(app)/loading.tsx

@@ -0,0 +1,12 @@
+import { Loader2 } from 'lucide-react'
+
+export default function AppLoading() {
+  return (
+    <div className="flex-1 flex items-center justify-center min-h-[50vh]">
+      <div className="flex flex-col items-center gap-3">
+        <Loader2 className="w-8 h-8 text-primary animate-spin" />
+        <p className="text-sm text-muted-foreground font-mono">Loading...</p>
+      </div>
+    </div>
+  )
+}