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)/meal-plan/page.tsx

@@ -3,9 +3,10 @@ import { headers } from "next/headers";
 import Link from "next/link";
 import { ChevronLeft, ChevronRight, ShoppingCart, Printer } from "lucide-react";
 import { auth } from "@/lib/auth/server";
-import { db, mealPlans, recipes, eq, and, desc } from "@epicure/db";
+import { db, mealPlans, mealPlanMembers, recipes, eq, and, desc } from "@epicure/db";
 import { buttonVariants } from "@/components/ui/button";
 import { MealPlanner } from "@/components/meal-plan/meal-planner";
+import { ShareMealPlanButton } from "@/components/meal-plan/share-meal-plan-button";
 import { WeeklyNutritionBar } from "@/components/nutrition/weekly-nutrition-bar";
 import { cn } from "@/lib/utils";
 
@@ -47,7 +48,7 @@ export default async function MealPlanPage({
   const sunday = addWeeks(monday, 1);
   sunday.setDate(sunday.getDate() - 1);
 
-  const [plan, userRecipes] = await Promise.all([
+  const [plan, userRecipes, sharedMemberships] = await Promise.all([
     db.query.mealPlans.findFirst({
       where: and(eq(mealPlans.userId, session.user.id), eq(mealPlans.weekStart, weekStart)),
       with: {
@@ -61,6 +62,10 @@ export default async function MealPlanPage({
       orderBy: desc(recipes.updatedAt),
       columns: { id: true, title: true },
     }),
+    db.query.mealPlanMembers.findMany({
+      where: eq(mealPlanMembers.userId, session.user.id),
+      with: { mealPlan: { with: { user: true } } },
+    }),
   ]);
 
   const entries = (plan?.entries ?? []).map((e) => ({
@@ -76,12 +81,13 @@ export default async function MealPlanPage({
 
   return (
     <div className="space-y-6">
-      <div className="flex items-center justify-between">
+      <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
         <div>
           <h1 className="text-3xl font-bold tracking-tight">Meal Plan</h1>
           <p className="text-muted-foreground mt-1">{label}</p>
         </div>
-        <div className="flex items-center gap-2">
+        <div className="flex flex-wrap items-center gap-2">
+          <ShareMealPlanButton weekStart={weekStart} />
           <Link href="/shopping-lists" className={cn(buttonVariants({ variant: "outline", size: "sm" }))}>
             <ShoppingCart className="h-4 w-4" />
             Shopping lists
@@ -101,6 +107,26 @@ export default async function MealPlanPage({
 
       <WeeklyNutritionBar weekStart={weekStart} />
       <MealPlanner weekStart={weekStart} initialEntries={entries} userRecipes={userRecipes} />
+
+      {sharedMemberships.length > 0 && (
+        <div className="space-y-3">
+          <h2 className="text-sm font-semibold text-muted-foreground">Shared with you</h2>
+          <div className="space-y-2 max-w-lg">
+            {sharedMemberships.map((m) => (
+              <Link
+                key={m.id}
+                href={`/meal-plan/shared/${m.mealPlan.id}`}
+                className="flex items-center justify-between rounded-xl border p-4 hover:shadow-sm transition-shadow"
+              >
+                <div>
+                  <p className="font-medium">{`${m.mealPlan.user?.name ?? "Unknown"}'s plan`}</p>
+                  <p className="text-sm text-muted-foreground">Week of {m.mealPlan.weekStart} · {m.role}</p>
+                </div>
+              </Link>
+            ))}
+          </div>
+        </div>
+      )}
     </div>
   );
 }

apps/web/app/(app)/meal-plan/shared/[mealPlanId]/page.tsx

@@ -0,0 +1,55 @@
+import type { Metadata } from "next";
+import { notFound } from "next/navigation";
+import { headers } from "next/headers";
+import { auth } from "@/lib/auth/server";
+import { db, mealPlans, recipes, eq, desc } from "@epicure/db";
+import { getMealPlanAccessById, canWriteMealPlan } from "@/lib/meal-plan-access";
+import { SharedMealPlanView } from "@/components/meal-plan/shared-meal-plan-view";
+
+type Params = { params: Promise<{ mealPlanId: string }> };
+
+export const metadata: Metadata = { title: "Shared Meal Plan" };
+
+export default async function SharedMealPlanPage({ params }: Params) {
+  const { mealPlanId } = await params;
+  const session = await auth.api.getSession({ headers: await headers() });
+  if (!session) return null;
+
+  const access = await getMealPlanAccessById(mealPlanId, session.user.id);
+  if (!access) notFound();
+
+  const plan = await db.query.mealPlans.findFirst({
+    where: eq(mealPlans.id, mealPlanId),
+    with: { entries: { with: { recipe: true } }, user: true },
+  });
+  if (!plan) notFound();
+
+  const userRecipes = await db.query.recipes.findMany({
+    where: eq(recipes.authorId, session.user.id),
+    orderBy: desc(recipes.updatedAt),
+    columns: { id: true, title: true },
+  });
+
+  const canEdit = canWriteMealPlan(access.role);
+
+  return (
+    <div className="space-y-6">
+      <div>
+        <h1 className="text-3xl font-bold tracking-tight">{`${plan.user?.name ?? "Shared"}'s Meal Plan`}</h1>
+        <p className="text-muted-foreground mt-1">Week of {plan.weekStart} · {access.role}</p>
+      </div>
+      <SharedMealPlanView
+        mealPlanId={mealPlanId}
+        canEdit={canEdit}
+        userRecipes={userRecipes}
+        initialEntries={plan.entries.map((e) => ({
+          id: e.id,
+          day: e.day,
+          mealType: e.mealType,
+          servings: e.servings,
+          recipe: e.recipe ? { id: e.recipe.id, title: e.recipe.title } : null,
+        }))}
+      />
+    </div>
+  );
+}