feat: per-tier feature toggles for recipe variations/pairings (v0.50.0)

Admins can now disable specific AI features per tier from Admin > Tier
Limits — new feature_flags table (feature x tier -> enabled, defaulting
to true so adding a new gated feature never needs a backfill).

Covers recipe variations, drink pairing, and meal pairing to start.
When disabled for a user's tier, the button stays visible (with a small
lock badge) but opens an upgrade dialog instead of running; the API
route rejects the call server-side either way (requireFeatureEnabled,
re-reads tier from the DB rather than trusting the session's cache,
same rationale as checkAndIncrementTierLimit).

The upgrade dialog is informational only — no Stripe checkout exists
yet (STRIPE_PLAN.md is still just a plan) — its CTA links to /support
prefilled as an upgrade-interest suggestion.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/changelog.ts

@@ -1,5 +1,5 @@
 // Mirrors CHANGELOG.md at the repo root — update both together.
-export const APP_VERSION = "0.49.1";
+export const APP_VERSION = "0.50.0";
 
 export type ChangelogEntry = {
   version: string;
@@ -11,6 +11,13 @@ export type ChangelogEntry = {
 };
 
 export const CHANGELOG: ChangelogEntry[] = [
+  {
+    version: "0.50.0",
+    date: "2026-07-18 14:20",
+    added: [
+      "Per-tier feature toggles, managed from Admin > Tier Limits. Recipe variations, drink pairing, and meal pairing can each be disabled for a tier (e.g. Free) — the buttons stay visible but show an upgrade prompt instead of running, and the API rejects the call server-side either way.",
+    ],
+  },
   {
     version: "0.49.1",
     date: "2026-07-18 13:10",