task-283(后台迁移收尾/发布): admin-vue 后台工程入库 + Flask 后台整体退役

- 新后台 admin-frontend-vue 整工程入库(base=/admin-vue/、History 路由、Nginx 静态托管方案与 verify-dist 校验)
- Java AdminConsoleController 改为入口重定向: /admin|/admin.html、/login|/login.html -> /admin-vue/; 删除 classpath:static 旧 admin.html/login.html 单页与 admin.js 副本
- Flask 后台整体退役: 删除 admin_api/auth/main 蓝图、web_source 页面、static 脚本与 admin 相关测试; app.py 收敛为仅注册 version_bp(/api/version、/api/version/latest, 供桌面端更新检查)
- AdminApiGuardFilterTest 豁免样例路径 /admin.html -> /admin-vue/

backend-java/src/test/java/com/nanri/aiimage/config/AdminApiGuardFilterTest.java

@@ -37,7 +37,7 @@ class AdminApiGuardFilterTest {
     void nonAdminApiPathIsNotGuarded() throws Exception {
         AdminAuthSupport authSupport = mock(AdminAuthSupport.class);
         AdminApiGuardFilter filter = newFilter(authSupport, true, "");
-        MockHttpServletRequest request = new MockHttpServletRequest("GET", "/admin.html");
+        MockHttpServletRequest request = new MockHttpServletRequest("GET", "/admin-vue/");
         MockHttpServletResponse response = new MockHttpServletResponse();
         MockFilterChain chain = new MockFilterChain();