feat: add static sitemap entry allowlist (no auth pages)

lib/sitemap/build-static-entries.ts

@@ -0,0 +1,50 @@
+import type { MetadataRoute } from "next"
+
+const BASE_URL = "https://deckyvault.xyz"
+
+/**
+ * Builds static sitemap entries for publicly-indexable pages.
+ *
+ * Auth pages (`/login`, `/signup`) are intentionally excluded because
+ * they provide no indexable content. Search engines should not surface
+ * authentication flows as standalone results.
+ *
+ * Also excluded: `/manage` (admin dashboard, noindex), `/search`
+ * (parameterized results, no canonical representation), `/profile`
+ * (user-specific), `/compare` (parameterized tool), and any `/api/*`
+ * routes (robots.txt disallow).
+ */
+export function buildStaticEntries(): MetadataRoute.Sitemap {
+  return [
+    {
+      url: BASE_URL,
+      lastModified: new Date(),
+      changeFrequency: "weekly" as const,
+      priority: 1,
+    },
+    {
+      url: `${BASE_URL}/games`,
+      lastModified: new Date(),
+      changeFrequency: "daily" as const,
+      priority: 0.8,
+    },
+    {
+      url: `${BASE_URL}/devices`,
+      lastModified: new Date(),
+      changeFrequency: "monthly" as const,
+      priority: 0.6,
+    },
+    {
+      url: `${BASE_URL}/updates`,
+      lastModified: new Date(),
+      changeFrequency: "weekly" as const,
+      priority: 0.5,
+    },
+    {
+      url: `${BASE_URL}/contact`,
+      lastModified: new Date(),
+      changeFrequency: "yearly" as const,
+      priority: 0.3,
+    },
+  ]
+}