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/android/app/build.gradle

@@ -10,7 +10,7 @@ android {
 
     defaultConfig {
         applicationId 'com.showen.flutter'
-        minSdkVersion 21
+        minSdkVersion flutter.minSdkVersion
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutter.versionCode
         versionName flutter.versionName

clients/flutter/android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java

@@ -0,0 +1,24 @@
+package io.flutter.plugins;
+
+import androidx.annotation.Keep;
+import androidx.annotation.NonNull;
+import io.flutter.Log;
+
+import io.flutter.embedding.engine.FlutterEngine;
+
+/**
+ * Generated file. Do not edit.
+ * This file is generated by the Flutter tool based on the
+ * plugins that support the Android platform.
+ */
+@Keep
+public final class GeneratedPluginRegistrant {
+  private static final String TAG = "GeneratedPluginRegistrant";
+  public static void registerWith(@NonNull FlutterEngine flutterEngine) {
+    try {
+      flutterEngine.getPlugins().add(new com.lib.flutter_blue_plus.FlutterBluePlusPlugin());
+    } catch (Exception e) {
+      Log.e(TAG, "Error registering plugin flutter_blue_plus_android, com.lib.flutter_blue_plus.FlutterBluePlusPlugin", e);
+    }
+  }
+}