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/components/recipe/variations-button.tsx

@@ -2,10 +2,11 @@
 
 import { useState } from "react";
 import { useTranslations } from "next-intl";
-import { GitBranch } from "lucide-react";
+import { GitBranch, Lock } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from "@/components/ui/tooltip";
 import { VariationsDialog } from "./variations-dialog";
+import { UpgradeDialog } from "@/components/premium/upgrade-dialog";
 
 export function VariationsButton({
   recipeId,
@@ -15,6 +16,7 @@ export function VariationsButton({
   cookMins,
   ingredients,
   steps,
+  locked = false,
 }: {
   recipeId: string;
   baseServings: number;
@@ -23,17 +25,26 @@ export function VariationsButton({
   cookMins?: number | null;
   ingredients: Array<{ rawName: string; quantity?: string | number | null; unit?: string | null; note?: string | null; order: number }>;
   steps: Array<{ instruction: string; timerSeconds?: number | null; order: number }>;
+  locked?: boolean;
 }) {
   const t = useTranslations("recipe");
   const [open, setOpen] = useState(false);
+  const [upgradeOpen, setUpgradeOpen] = useState(false);
 
   return (
     <>
       <TooltipProvider>
         <Tooltip>
           <TooltipTrigger render={
-            <Button variant="ghost" size="icon" onClick={() => setOpen(true)} aria-label={t("variationsTooltip")}>
+            <Button
+              variant="ghost"
+              size="icon"
+              onClick={() => (locked ? setUpgradeOpen(true) : setOpen(true))}
+              aria-label={t("variationsTooltip")}
+              className="relative"
+            >
               <GitBranch className="h-4 w-4" />
+              {locked && <Lock className="h-2.5 w-2.5 absolute bottom-1 right-1 text-muted-foreground" />}
             </Button>
           } />
           <TooltipContent>{t("variationsTooltip")}</TooltipContent>
@@ -50,6 +61,12 @@ export function VariationsButton({
         open={open}
         onOpenChange={setOpen}
       />
+      <UpgradeDialog
+        open={upgradeOpen}
+        onOpenChange={setUpgradeOpen}
+        featureKey="recipe_variations"
+        featureLabel="Recipe variations"
+      />
     </>
   );
 }