refactor: 迁移根目录 docker/ 到 source/docker/，更新所有路径引用

- 将 docker/{nginx.conf,run.sh,zz-phprun.ini,zz-phpfpm.conf} 移动到 source/docker/
- 更新所有 Dockerfile 中 /var/www/html/docker/ -> /var/www/html/source/docker/
- 更新 stack.json managed_files 路径前缀
- 重组 stack 模式目录结构 docker/ -> source/docker/
- 更新 source/README.md 目录描述
- 更新 AdminUpdateServiceBase.php 可选文件前缀

source/stack/stack.json

@@ -6,9 +6,9 @@
     ".gitea/workflows/build-and-deploy.yml",
     ".docker-dev.env",
     ".dockerignore",
-    "docker/zzz-dev.ini",
-    "docker/zzz-xdebug.ini",
-    "docker/run.sh"
+    "source/docker/zzz-dev.ini",
+    "source/docker/zzz-xdebug.ini",
+    "source/docker/run.sh"
   ],
   "modes": {
     "default": {