refactor(data): add mock API adapters, id utility, and toast feedback

lib/api/comments.ts

@@ -0,0 +1,9 @@
+import { mockComments } from "@/lib/mock"
+
+export function listComments() {
+  return mockComments
+}
+
+export function listCommentsByPost(postId: string) {
+  return mockComments.filter((comment) => comment.postId === postId)
+}