feat: implement remaining TODO.md feature ideas + fix mobile headers

Implements the six previously-unscoped feature ideas plus a mobile
layout fix reported via screenshot:

- Mobile: Recipes/Collections/Pantry/Meal Plan/Shopping Lists headers
  now stack and wrap instead of clipping buttons on narrow viewports.
- Recipe diff/compare view: word/list diff against any past version,
  next to Restore in version history.
- Shared meal plans & shopping lists: new shoppingListMembers/
  mealPlanMembers tables (viewer/editor roles, mirrors
  collectionMembers), share dialogs, membership-checked routes.
- PDF cookbook export: /print/collection/[id] renders a whole
  collection with page breaks, using the existing print-CSS pattern
  instead of adding a PDF rendering dependency.
- Grocery delivery handoff: shopping lists can copy-as-text (works
  today) or send to Instacart once INSTACART_API_KEY is configured
  (stub adapter — real API needs a partner agreement).
- Personalized "For You" feed tab: ranks public recipes by tag/
  dietary overlap with the user's favorited/highly-rated history.
- PWA: added manifest.json + icons on top of the existing service
  worker so the app is installable; cook-mode pages were already
  cached for offline use.

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

apps/web/app/(app)/recipes/can-cook/page.tsx

@@ -8,6 +8,14 @@ import { CanCookContent } from "@/components/recipe/can-cook-content";
 
 export const metadata: Metadata = { title: "What can I cook?" };
 
+const EXPIRING_WITHIN_DAYS = 3;
+
+function isExpiringSoon(expiresAt: Date | null): boolean {
+  if (!expiresAt) return false;
+  const days = Math.ceil((expiresAt.getTime() - Date.now()) / (1000 * 60 * 60 * 24));
+  return days >= 0 && days <= EXPIRING_WITHIN_DAYS;
+}
+
 export default async function CanCookPage() {
   const session = await auth.api.getSession({ headers: await headers() });
   if (!session) return null;
@@ -27,6 +35,12 @@ export default async function CanCookPage() {
 
   const pantryKeys = new Set(pantry.map((p) => p.rawName.toLowerCase()));
 
+  const expiringSoonKeys = new Set(
+    pantry
+      .filter((p) => isExpiringSoon(p.expiresAt))
+      .map((p) => p.rawName.toLowerCase())
+  );
+
   const scored = userRecipes
     .filter((r) => r.ingredients.length > 0)
     .map((recipe) => {
@@ -37,6 +51,9 @@ export default async function CanCookPage() {
         .filter((ing) => !pantryKeys.has(ing.rawName.toLowerCase()))
         .map((ing) => ing.rawName)
         .slice(0, 5);
+      const usesExpiring = recipe.ingredients
+        .filter((ing) => expiringSoonKeys.has(ing.rawName.toLowerCase()))
+        .map((ing) => ing.rawName);
       const total = recipe.ingredients.length;
       const cover = recipe.photos?.find((p) => p.isCover) ?? recipe.photos?.[0];
       return {
@@ -50,9 +67,15 @@ export default async function CanCookPage() {
         total,
         pct: Math.round((matched / total) * 100),
         missing,
+        usesExpiring,
       };
     })
-    .sort((a, b) => b.pct - a.pct);
+    .sort((a, b) => {
+      if (a.usesExpiring.length > 0 !== b.usesExpiring.length > 0) {
+        return a.usesExpiring.length > 0 ? -1 : 1;
+      }
+      return b.pct - a.pct;
+    });
 
   return <CanCookContent pantryCount={pantry.length} scored={scored} />;
 }