feat: comprehensive application audit and fixes

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

Co-authored-by: Moheeb Zara <1184415+virgilvox@users.noreply.github.com>

app/loading.tsx

@@ -0,0 +1,18 @@
+export default function Loading() {
+  return (
+    <div className="min-h-screen bg-background flex items-center justify-center">
+      <div className="flex flex-col items-center gap-4">
+        <div className="w-10 h-10 rounded bg-primary flex items-center justify-center animate-pulse">
+          <span className="text-primary-foreground font-mono text-sm font-bold">
+            {'{'}<span>hs</span>{'}'}
+          </span>
+        </div>
+        <div className="flex gap-1">
+          <div className="w-2 h-2 rounded-full bg-primary animate-bounce [animation-delay:-0.3s]" />
+          <div className="w-2 h-2 rounded-full bg-primary animate-bounce [animation-delay:-0.15s]" />
+          <div className="w-2 h-2 rounded-full bg-primary animate-bounce" />
+        </div>
+      </div>
+    </div>
+  )
+}