feat: 6 new per-tier feature flags (off by default) + flag-icon locale switcher + hide BYOK when disabled (v0.74.0)

Extends the existing feature-flags system (previously 3 keys, all
default-enabled) with 6 more: recipe_import_url, recipe_import_photo,
nutrition_estimation, markdown_export, weekly_nutrition,
grocery_delivery. Each FEATURE_DEFINITIONS entry now carries its own
defaultEnabled -- the new 6 default to false, the original 3 stay
true -- so no migration/seed was needed for the "off by default"
requirement, just a per-key fallback instead of a blanket true.

Gated server-side (requireFeatureEnabledResponse, a new shared
helper avoiding six copies of the same try/catch) on: import-url,
import-photo, nutrition POST estimate, bulk markdown export, weekly
meal-plan nutrition GET, Instacart export. Gated client-side by
hiding the trigger entirely (not just disabling) on every page that
renders one: recipe detail (meal/drink pairing buttons, nutrition
panel's estimate button, markdown export), recipes list (import-URL
button, including the OS Share Target auto-import path), new-recipe
page (photo import), meal-plan page (markdown export, weekly
nutrition bar), shopping-list/collection/pantry pages (markdown
export), shopping-list page (Instacart button, now gated by both the
existing env-var check AND the tier flag).

Also: BYOK section on Settings -> AI now hidden entirely for
non-BYOK users (previously showed a locked-and-teased notice, same
inconsistency the Model Prefs fix closed yesterday). Language
switcher shows a flag icon (FlagGB/FlagFR, moved from
components/marketing to components/shared so both the logged-in
settings switcher and the logged-out marketing one can use it)
instead of plain "English"/"Français" text-only options.

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

apps/web/lib/feature-flags.ts

@@ -1,3 +1,4 @@
+import { NextResponse } from "next/server";
 import { db, featureFlags, users, eq, and } from "@epicure/db";
 
 export type Tier = "free" | "pro" | "family";
@@ -8,19 +9,64 @@ export const FEATURE_DEFINITIONS = [
     key: "recipe_variations",
     label: "Recipe variations",
     description: "AI-generated variations of a recipe (dietary swaps, flavor twists, etc.).",
+    defaultEnabled: true,
   },
   {
     key: "drink_pairing",
     label: "Drink pairing",
     description: "AI-suggested drink pairings for a recipe.",
+    defaultEnabled: true,
   },
   {
     key: "meal_pairing",
     label: "Meal pairing",
     description: "AI-suggested side dish / meal pairings for a recipe.",
+    defaultEnabled: true,
+  },
+  // The following ship disabled by default (2026-07-24) — turn on per tier
+  // from this page once ready, rather than a code change.
+  {
+    key: "recipe_import_url",
+    label: "Import from URL",
+    description: "Import a recipe by pasting a link to another site.",
+    defaultEnabled: false,
+  },
+  {
+    key: "recipe_import_photo",
+    label: "Import from photo",
+    description: "Import a recipe by photographing a cookbook page or handwritten card.",
+    defaultEnabled: false,
+  },
+  {
+    key: "nutrition_estimation",
+    label: "Nutrition estimation",
+    description: "AI/USDA-estimated nutrition facts for a recipe.",
+    defaultEnabled: false,
+  },
+  {
+    key: "markdown_export",
+    label: "Markdown export",
+    description: "Export a recipe, collection, meal plan, or pantry list as Markdown.",
+    defaultEnabled: false,
+  },
+  {
+    key: "weekly_nutrition",
+    label: "Weekly nutrition",
+    description: "Nutrition rollup across a whole meal-plan week.",
+    defaultEnabled: false,
+  },
+  {
+    key: "grocery_delivery",
+    label: "Grocery delivery integration",
+    description: "Export a shopping list to a grocery delivery provider (e.g. Instacart).",
+    defaultEnabled: false,
   },
 ] as const;
 
+const DEFAULT_ENABLED: Record<string, boolean> = Object.fromEntries(
+  FEATURE_DEFINITIONS.map((f) => [f.key, f.defaultEnabled])
+);
+
 export type FeatureKey = (typeof FEATURE_DEFINITIONS)[number]["key"];
 export const FEATURE_KEYS = FEATURE_DEFINITIONS.map((f) => f.key) as FeatureKey[];
 
@@ -41,7 +87,7 @@ export async function getFeatureFlagMatrix(): Promise<Record<FeatureKey, Record<
   for (const key of FEATURE_KEYS) {
     matrix[key] = {} as Record<Tier, boolean>;
     for (const tier of TIERS) {
-      matrix[key][tier] = overrides.get(`${key}:${tier}`) ?? true;
+      matrix[key][tier] = overrides.get(`${key}:${tier}`) ?? DEFAULT_ENABLED[key] ?? true;
     }
   }
   return matrix;
@@ -67,7 +113,7 @@ export async function isFeatureEnabledForTier(featureKey: FeatureKey, tier: Tier
     .select({ enabled: featureFlags.enabled })
     .from(featureFlags)
     .where(and(eq(featureFlags.featureKey, featureKey), eq(featureFlags.tier, tier)));
-  return row ? row.enabled : true;
+  return row ? row.enabled : (DEFAULT_ENABLED[featureKey] ?? true);
 }
 
 /**
@@ -81,3 +127,21 @@ export async function requireFeatureEnabled(userId: string, featureKey: FeatureK
   const enabled = await isFeatureEnabledForTier(featureKey, tier);
   if (!enabled) throw new FeatureDisabledError(featureKey);
 }
+
+/** Route-level convenience: returns the 403 response to return early, or
+ * null if the feature is enabled — avoids repeating the same try/catch
+ * around requireFeatureEnabled in every gated route. */
+export async function requireFeatureEnabledResponse(userId: string, featureKey: FeatureKey): Promise<NextResponse | null> {
+  try {
+    await requireFeatureEnabled(userId, featureKey);
+    return null;
+  } catch (err) {
+    if (err instanceof FeatureDisabledError) {
+      return NextResponse.json(
+        { error: "This feature isn't available on your plan", code: "FEATURE_DISABLED", featureKey: err.featureKey },
+        { status: 403 }
+      );
+    }
+    throw err;
+  }
+}