Sync layouts, typography, and watermark studio for self-hosted OSS.

Unlock features without credits/Stripe, point docs to docs.songs2vid.com, and drop leftover billing admin surfaces.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/entitlements.ts

@@ -0,0 +1,41 @@
+import { Plan } from "@prisma/client";
+import type { LayoutSettings } from "./layout";
+import {
+  PREMIUM_REQUIRED_CODE,
+  type WatermarkSettings,
+} from "./watermark";
+
+export class PremiumRequiredError extends Error {
+  readonly code = PREMIUM_REQUIRED_CODE;
+  readonly status = 403;
+  constructor(message: string) {
+    super(message);
+    this.name = "PremiumRequiredError";
+  }
+}
+
+/** OSS: all watermark / typography features unlocked. */
+export function assertCustomWatermarkAllowed(_plan: Plan, _settings: WatermarkSettings) {
+  return;
+}
+
+/** OSS: all art-track layout features unlocked. */
+export function assertArtTrackLayoutAllowed(_plan: Plan, _settings: LayoutSettings) {
+  return;
+}
+
+/** OSS: per-track cover images always allowed. */
+export function assertPerItemImagesAllowed(
+  _plan: Plan,
+  _sharedImagePath: string,
+  _itemImagePaths: Array<string | null | undefined>,
+) {
+  return;
+}
+
+export function premiumRequiredResponse(message: string) {
+  return {
+    error: message,
+    code: PREMIUM_REQUIRED_CODE,
+  };
+}