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/settings/settings-form.tsx

@@ -10,8 +10,11 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@
 import { Switch } from "@/components/ui/switch";
 import { useTranslations } from "next-intl";
 import { useLocale, SUPPORTED_LOCALES, type Locale } from "@/lib/i18n/provider";
+import { FlagGB, FlagFR } from "@/components/shared/flag-icons";
 import { AvatarUploader } from "./avatar-uploader";
 
+const LOCALE_FLAGS: Record<Locale, typeof FlagGB> = { en: FlagGB, fr: FlagFR };
+
 const USERNAME_PATTERN = /^[a-z0-9_]{3,20}$/;
 
 type UserProps = {
@@ -282,11 +285,17 @@ export function SettingsForm({ user }: { user: UserProps }) {
             <SelectValue />
           </SelectTrigger>
           <SelectContent>
-            {SUPPORTED_LOCALES.map((l) => (
-              <SelectItem key={l.code} value={l.code}>
-                {l.label}
-              </SelectItem>
-            ))}
+            {SUPPORTED_LOCALES.map((l) => {
+              const Flag = LOCALE_FLAGS[l.code];
+              return (
+                <SelectItem key={l.code} value={l.code}>
+                  <span className="flex items-center gap-2">
+                    <Flag className="h-3 w-4 rounded-[2px]" />
+                    {l.label}
+                  </span>
+                </SelectItem>
+              );
+            })}
           </SelectContent>
         </Select>
       </section>