v3: added an "in collections" section to dump pages, listing the collections a dump belongs to

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

api/routes/dumps.ts

@@ -8,6 +8,7 @@ import {
   isCreateUrlDumpRequest,
   isUpdateDumpRequest,
   type PaginatedData,
+  type Playlist,
 } from "../model/interfaces.ts";
 
 import { authMiddleware } from "../middleware/auth.ts";
@@ -30,6 +31,7 @@ import {
 } from "../services/dump-service.ts";
 import { getDumpVoters } from "../services/vote-service.ts";
 import { getRelatedDumps } from "../services/backlink-service.ts";
+import { getPlaylistsForDump } from "../services/playlist-service.ts";
 
 const router = new Router({ prefix: "/api/dumps" });
 
@@ -128,6 +130,18 @@ router.get("/:dumpId/related", async (ctx) => {
   ctx.response.body = responseBody;
 });
 
+router.get("/:dumpId/playlists", async (ctx) => {
+  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
+  // Resolve through getDump so private dumps 404 for anyone but their owner.
+  const dump = getDump(ctx.params.dumpId, requestingUserId);
+  const playlists = getPlaylistsForDump(dump.id, requestingUserId);
+  const responseBody: APIResponse<Playlist[]> = {
+    success: true,
+    data: playlists,
+  };
+  ctx.response.body = responseBody;
+});
+
 router.get("/", async (ctx) => {
   const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
   const { page, limit } = parsePagination(ctx.request.url.searchParams);