chore: 修正构建配置以支持本机 JDK 25 构建

- 移除 toolchain 约束，改用 options.release = 21 兼容 Halo API
- 通过 gradle.properties 指定本机 JDK 25 路径
- gradle wrapper 切换至腾讯镜像源解决下载超时

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

build.gradle

@@ -23,12 +23,6 @@ test {
     useJUnitPlatform()
 }
 
-java {
-    toolchain {
-        languageVersion = JavaLanguageVersion.of(21)
-    }
-}
-
 tasks.withType(JavaCompile).configureEach {
     options.encoding = "UTF-8"
     options.release = 21