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)/meal-plan/page.tsx

@@ -12,6 +12,7 @@ import { NewShoppingListButton } from "@/components/meal-plan/new-shopping-list-
 import { WeeklyNutritionBar } from "@/components/nutrition/weekly-nutrition-bar";
 import { cn } from "@/lib/utils";
 import { ExportMarkdownButton } from "@/components/shared/export-markdown-button";
+import { getFeatureFlagMatrix, type Tier } from "@/lib/feature-flags";
 import { mealPlanToMarkdown } from "@/lib/markdown/meal-plan";
 import { getMessages, formatMessage } from "@/lib/i18n/server";
 
@@ -59,6 +60,10 @@ export default async function MealPlanPage({
   const session = await auth.api.getSession({ headers: await headers() });
   if (!session) return null;
   const msgs = getMessages((session.user as { locale?: string }).locale);
+  const viewerTier = (session.user as { tier?: string }).tier as Tier | undefined ?? "free";
+  const featureFlags = await getFeatureFlagMatrix();
+  const canExportMarkdown = featureFlags.markdown_export[viewerTier];
+  const canSeeWeeklyNutrition = featureFlags.weekly_nutrition[viewerTier];
 
   const monday = getMonday(week);
   const weekStart = toDateStr(monday);
@@ -157,10 +162,12 @@ export default async function MealPlanPage({
             } />
             <TooltipContent>{msgs.common.print}</TooltipContent>
           </Tooltip>
-          <ExportMarkdownButton
-            markdown={mealPlanToMarkdown({ label, entries })}
-            filename={`meal-plan-${weekStart}`}
-          />
+          {canExportMarkdown && (
+            <ExportMarkdownButton
+              markdown={mealPlanToMarkdown({ label, entries })}
+              filename={`meal-plan-${weekStart}`}
+            />
+          )}
           <Tooltip>
             <TooltipTrigger render={
               <a href={`/api/v1/meal-plans/${weekStart}/export/ics`} className={cn(buttonVariants({ variant: "ghost", size: "icon" }))} aria-label={msgs.mealPlan.exportCalendar}>
@@ -173,7 +180,7 @@ export default async function MealPlanPage({
       </div>
       </TooltipProvider>
 
-      <WeeklyNutritionBar weekStart={weekStart} />
+      {canSeeWeeklyNutrition && <WeeklyNutritionBar weekStart={weekStart} />}
       <MealPlanner weekStart={weekStart} initialEntries={entries} userRecipes={userRecipes} hasNutritionGoals={hasNutritionGoals} />
 
       {sharedMemberships.length > 0 && (