refactor(api)!: 平台 id 回退——joox/5sing/bili/apple 恢复全名，目录对齐 bd/mg

- 撤销 3381e9b/1b972ec 中 jx/5s/bl/ap 四个短码，恢复 joox/5sing/bili/apple；
  qian→bd、migu→mg 保留
- 目录与文件对齐保留的新 id：sdk/qian/→sdk/bd/、sdk/migu/→sdk/mg/、
  sdk/apis/qian.ts→bd.ts、migu.ts→mg.ts、src/http/migu-stream.ts→mg-stream.ts
  （规则改为「目录=对外 id」，聚合入口的模块变量同步更名；music.migu.cn 等域名、
  上游 music-lib 对照注释、miguGet 等功能标识符不动）
- 对外 id 全表：kw kg tx wy qs xm me qt lr mg bd joox 5sing bili apple

**破坏性变更**：joox/5sing/bili/apple 四平台的 URL、/sources 返回与
data/auth.json 凭据键恢复全名，已存短码键的登录态需重新登录。

验证：typecheck ✓、pnpm test 112/112 ✓

sdk/apple/musicSearch.ts

@@ -39,7 +39,7 @@ export const search = async(keyword: string, page = 1, limit = 20) => {
     allPage: hasNext ? p + 1 : p,
     total: (p - 1) * l + list.length,
     limit: l,
-    source: 'ap' as const,
+    source: 'apple' as const,
   }
 }
 
@@ -53,7 +53,7 @@ export const searchAlbum = async(keyword: string, page = 1, limit = 20) => {
     total: (p - 1) * l + list.length,
     page: p,
     limit: l,
-    source: 'ap' as const,
+    source: 'apple' as const,
   }
 }
 
@@ -67,7 +67,7 @@ export const searchPlaylist = async(keyword: string, page = 1, limit = 20) => {
     total: (p - 1) * l + list.length,
     page: p,
     limit: l,
-    source: 'ap' as const,
+    source: 'apple' as const,
   }
 }