refactor: 完全重构为 Anki 兼容数据结构

- 用 Deck 替换 Folder
- 用 Note + Card 替换 Pair (双向复习)
- 添加 NoteType (卡片模板)
- 添加 Revlog (复习历史)
- 实现 SM-2 间隔重复算法
- 更新所有前端页面
- 添加数据库迁移

src/app/(features)/explore/[id]/page.tsx

@@ -1,8 +1,8 @@
 import { redirect } from "next/navigation";
 import { ExploreDetailClient } from "./ExploreDetailClient";
-import { actionGetPublicFolderById } from "@/modules/folder/folder-action";
+import { actionGetPublicDeckById } from "@/modules/deck/deck-action";
 
-export default async function ExploreFolderPage({
+export default async function ExploreDeckPage({
   params,
 }: {
   params: Promise<{ id: string }>;
@@ -13,11 +13,11 @@ export default async function ExploreFolderPage({
     redirect("/explore");
   }
 
-  const result = await actionGetPublicFolderById(Number(id));
+  const result = await actionGetPublicDeckById({ deckId: Number(id) });
 
   if (!result.success || !result.data) {
     redirect("/explore");
   }
 
-  return <ExploreDetailClient folder={result.data} />;
+  return <ExploreDetailClient deck={result.data} />;
 }