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/components/recipe/nutrition-panel.tsx

@@ -20,9 +20,13 @@ interface NutritionPanelProps {
   recipeId: string;
   initialData?: NutritionData | null;
   initialManual?: boolean;
+  /** AI/USDA estimation feature toggled off for this tier — hides the
+   * (re-)estimate action. Previously-stored data (manual or a past
+   * estimate) still displays; there's just no button to refresh it. */
+  estimateEnabled?: boolean;
 }
 
-export function NutritionPanel({ recipeId, initialData, initialManual }: NutritionPanelProps) {
+export function NutritionPanel({ recipeId, initialData, initialManual, estimateEnabled = true }: NutritionPanelProps) {
   const t = useTranslations("nutritionPanel");
   const [nutrition, setNutrition] = useState<NutritionData | null>(initialData ?? null);
   const [manual, setManual] = useState(!!initialManual);
@@ -50,6 +54,7 @@ export function NutritionPanel({ recipeId, initialData, initialManual }: Nutriti
   }
 
   if (!nutrition && !loading) {
+    if (!estimateEnabled) return null;
     return (
       <div className="flex flex-col gap-2">
         {error && <p className="text-sm text-destructive">{error}</p>}
@@ -65,15 +70,17 @@ export function NutritionPanel({ recipeId, initialData, initialManual }: Nutriti
       <CardHeader className="pb-3">
         <div className="flex items-center justify-between">
           <CardTitle className="text-base">{t("title")}</CardTitle>
-          <Button
-            variant="ghost"
-            size="sm"
-            onClick={handleEstimate}
-            disabled={loading}
-            className="text-xs text-muted-foreground"
-          >
-            {loading ? t("estimating") : manual ? t("estimateInsteadButton") : t("reEstimateButton")}
-          </Button>
+          {estimateEnabled && (
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={handleEstimate}
+              disabled={loading}
+              className="text-xs text-muted-foreground"
+            >
+              {loading ? t("estimating") : manual ? t("estimateInsteadButton") : t("reEstimateButton")}
+            </Button>
+          )}
         </div>
         {manual && !loading && (
           <p className="text-xs text-muted-foreground">{t("manualBadge")}</p>