feat: 添加 Caddy 反向代理配置示例及 TLS/SSL 文档

dashboard/docs/Caddyfile.docker.example

@@ -0,0 +1,12 @@
+maibot.example.com {
+    encode zstd gzip
+
+    header {
+        Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"
+        X-Content-Type-Options "nosniff"
+        X-Frame-Options "SAMEORIGIN"
+        Referrer-Policy "strict-origin-when-cross-origin"
+    }
+
+    reverse_proxy core:8001
+}