feat(social): follows, favorites, comments, reactions, collections, public profiles

Follow/unfollow users. Recipe favorites. Threaded comments with emoji reactions.
Collections (public/private) with shared member invite. Activity feed.
Public profile pages at /u/[username].

apps/web/app/api/v1/collections/[id]/fork/route.ts

@@ -0,0 +1,41 @@
+import { NextRequest, NextResponse } from "next/server";
+import { db, collections, collectionRecipes, eq, and, or } from "@epicure/db";
+import { requireSession } from "@/lib/api-auth";
+
+type Params = { params: Promise<{ id: string }> };
+
+export async function POST(_req: NextRequest, { params }: Params) {
+  const { session, response } = await requireSession();
+  if (response) return response;
+  const { id } = await params;
+
+  // Allow forking public collections or own collections
+  const source = await db.query.collections.findFirst({
+    where: and(
+      eq(collections.id, id),
+      or(eq(collections.isPublic, true), eq(collections.userId, session!.user.id))
+    ),
+    with: { recipes: { columns: { recipeId: true } } },
+  });
+
+  if (!source) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+  const newId = crypto.randomUUID();
+  await db.insert(collections).values({
+    id: newId,
+    userId: session!.user.id,
+    name: `${source.name} (fork)`,
+    description: source.description,
+    isPublic: false,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+  });
+
+  if (source.recipes.length > 0) {
+    await db.insert(collectionRecipes).values(
+      source.recipes.map((r) => ({ collectionId: newId, recipeId: r.recipeId }))
+    );
+  }
+
+  return NextResponse.json({ id: newId }, { status: 201 });
+}