fix: standardize locked-vs-hidden treatment across all 9 per-tier gated features (v0.79.0)

Rule, applied consistently everywhere via a new isFeatureAvailableAnyTier() helper: if a feature is enabled on at least one tier, it stays visible for locked-out viewers with a small "Pro" badge and opens an upgrade prompt on click; if a feature is disabled on every tier, it hides entirely, since there's no upgrade path to point at.

Covers: recipe variations, meal/drink pairings, nutrition estimation, Markdown export (5 call sites), weekly nutrition, import from URL, import from photo, and the Instacart grocery-delivery menu item. Previously inconsistent — some hid outright, one showed a lock icon overlapping its own icon.

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

apps/web/components/admin/feature-flags-form.tsx

@@ -48,7 +48,7 @@ export function FeatureFlagsForm({
       <div>
         <h2 className="font-semibold text-lg">Feature Toggles</h2>
         <p className="text-sm text-muted-foreground mt-1">
-          Disable a feature for a tier to hide it for that tier&apos;s users (most features hide entirely; recipe variations instead shows a &quot;Pro&quot; badge in its tooltip and opens an upgrade prompt — see each feature&apos;s actual behavior in the app).
+          Disable a feature for a tier to gate it for that tier&apos;s users. If the feature is still enabled on at least one other tier, it stays visible with a &quot;Pro&quot; upsell (clicking opens an upgrade prompt) — it only disappears entirely once every tier has it off, since at that point there&apos;s no upgrade path to point at.
         </p>
       </div>