fix: cap Prisma pool during next build to stop deploy SSG timeouts

Next build workers were each opening up to DATABASE_POOL_SIZE connections and exhausting MySQL (pool active=0), hanging sitemap generation. Cap build pool to 5, fail connect faster, limit SSG concurrency, and make sitemap dynamic.

Co-authored-by: Cursor <[email protected]>

src/lib/prisma-pool.ts

@@ -0,0 +1,16 @@
+/**
+ * Cap pool size during `next build` so N workers × pool don't exhaust MySQL.
+ * Kept free of Prisma/env imports so unit tests can exercise it in isolation.
+ */
+export function resolvePrismaConnectionLimit(
+	poolSize: number,
+	phase = process.env.NEXT_PHASE,
+): number {
+	if (
+		phase === "phase-production-build" ||
+		phase === "phase-production-compile"
+	) {
+		return Math.min(poolSize, 5);
+	}
+	return poolSize;
+}