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/app/(app)/recipes/[id]/page.tsx

@@ -114,6 +114,8 @@ export default async function RecipePage({ params }: Params) {
     variations: !featureFlags.recipe_variations[viewerTier],
     drinkPairing: !featureFlags.drink_pairing[viewerTier],
     mealPairing: !featureFlags.meal_pairing[viewerTier],
+    nutritionEstimation: !featureFlags.nutrition_estimation[viewerTier],
+    markdownExport: !featureFlags.markdown_export[viewerTier],
   };
 
   const isOwner = recipe.authorId === session.user.id;
@@ -188,8 +190,8 @@ export default async function RecipePage({ params }: Params) {
             <FavoriteButton recipeId={id} initialFavorited={isFavorited} />
             {!recipe.isBatchCook && recipe.recipeType !== "drink" && (
               <>
-                <MealPairingButton recipeId={id} locked={locked.mealPairing} />
-                <DrinkPairingButton recipeId={id} locked={locked.drinkPairing} />
+                {!locked.mealPairing && <MealPairingButton recipeId={id} locked={false} />}
+                {!locked.drinkPairing && <DrinkPairingButton recipeId={id} locked={false} />}
               </>
             )}
             {recipe.visibility === "public" && (
@@ -247,22 +249,24 @@ export default async function RecipePage({ params }: Params) {
             <ShareRecipeButton recipeId={id} visibility={recipe.visibility} />
             <SaveOfflineButton recipeId={id} recipeTitle={recipe.title} />
             <PrintButton recipeId={id} />
-            <ExportMarkdownButton
-              markdown={recipeToMarkdown({
-                title: recipe.title,
-                description: recipe.description,
-                baseServings: recipe.baseServings,
-                prepMins: recipe.prepMins,
-                cookMins: recipe.cookMins,
-                difficulty: recipe.difficulty,
-                sourceUrl: recipe.sourceUrl,
-                ingredients: recipe.ingredients,
-                steps: recipe.steps,
-                isBatchCook: recipe.isBatchCook,
-                batchDishes: recipe.batchDishes,
-              })}
-              filename={recipe.title}
-            />
+            {!locked.markdownExport && (
+              <ExportMarkdownButton
+                markdown={recipeToMarkdown({
+                  title: recipe.title,
+                  description: recipe.description,
+                  baseServings: recipe.baseServings,
+                  prepMins: recipe.prepMins,
+                  cookMins: recipe.cookMins,
+                  difficulty: recipe.difficulty,
+                  sourceUrl: recipe.sourceUrl,
+                  ingredients: recipe.ingredients,
+                  steps: recipe.steps,
+                  isBatchCook: recipe.isBatchCook,
+                  batchDishes: recipe.batchDishes,
+                })}
+                filename={recipe.title}
+              />
+            )}
             {isOwner && (
               <>
                 <VersionHistoryButton
@@ -419,7 +423,7 @@ export default async function RecipePage({ params }: Params) {
               order: ing.order,
             }))}
           />
-          <NutritionPanel recipeId={id} initialData={recipe.nutritionData} initialManual={recipe.nutritionManual} />
+          <NutritionPanel recipeId={id} initialData={recipe.nutritionData} initialManual={recipe.nutritionManual} estimateEnabled={!locked.nutritionEstimation} />
         </div>
       )}