refactor(frontend): share Clerk publishable-key heuristic across client+server

frontend/src/auth/clerkKey.ts

@@ -0,0 +1,22 @@
+// Shared Clerk publishable-key gating logic.
+//
+// IMPORTANT: keep this file dependency-free (no `"use client"`, no React, no Clerk imports)
+// so it can be used from both client and server/edge entrypoints.
+
+export function isLikelyValidClerkPublishableKey(key: string | undefined): key is string {
+  if (!key) return false;
+
+  // Clerk publishable keys look like: pk_test_... or pk_live_...
+  // In CI we want builds to stay secretless; if the key isn't present/valid,
+  // we skip Clerk entirely so `next build` can prerender.
+  //
+  // Note: this is a conservative heuristic (not an authoritative validation).
+  const m = /^pk_(test|live)_([A-Za-z0-9]+)$/.exec(key);
+  if (!m) return false;
+
+  const body = m[2];
+  if (body.length < 16) return false;
+  if (/^0+$/.test(body)) return false;
+
+  return true;
+}