feat: Flutter APK 编译成功 + Gradle 配置修复 + APK 下载部署 + 待优化清单

- 通过 qemu-user-static 实现 ARM64 主机编译 Android APK (51MB)
- 修复 Gradle: Aliyun 镜像 + PREFER_SETTINGS + JVM 内存 1536M
- 部署 APK 到 configs/downloads/, Web 下载接口已验证 (HTTP 200)
- 新增 Flutter TODO.md: 10项待优化 (P0/P1/P2 分级)
- 新增 pm_soul.md, 更新 routes.rs APK 下载路由

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

clients/flutter/lib/screens/settings_screen.dart

@@ -103,7 +103,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
                         Text('可用配置文件', style: Theme.of(context).textTheme.titleMedium),
                         const SizedBox(height: AppSpacing.md),
                         DropdownButtonFormField<String>(
-                          value: _activeConfig,
+                          initialValue: _activeConfig,
                           items: _availableConfigs
                               .map(
                                 (item) => DropdownMenuItem<String>(