chore: 初始提交 Fonu 1.0.2

- 公网反代：Nginx 状态卡片（版本 / 运行状态 / 配置校验 / 端口监听）
- 部署设置第一、二梯队（HTTPS 开关、安全头、限流、连接数、仅中国大陆 IP）
- 隧道检测兼容 frps v0.68 / v0.71（V2 与旧版端点）
- 恢复被清空的 internal/frp/store.go、internal/api/ddns_handler.go、web/src/views/DdnsView.vue

internal/api/response_test.go

@@ -0,0 +1,64 @@
+package api
+
+import (
+	"bytes"
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestWriteJSONNilSlice(t *testing.T) {
+	var items []string
+	rec := httptest.NewRecorder()
+	writeJSON(rec, http.StatusOK, items)
+
+	if rec.Body.String() != "[]" {
+		t.Fatalf("expected [], got %q", rec.Body.String())
+	}
+}
+
+func TestWriteJSONNilMap(t *testing.T) {
+	var values map[string]string
+	rec := httptest.NewRecorder()
+	writeJSON(rec, http.StatusOK, values)
+
+	if rec.Body.String() != "{}" {
+		t.Fatalf("expected {}, got %q", rec.Body.String())
+	}
+}
+
+func TestWriteJSONSlice(t *testing.T) {
+	rec := httptest.NewRecorder()
+	writeJSON(rec, http.StatusOK, []int{1, 2})
+
+	var out []int
+	if err := json.Unmarshal(rec.Body.Bytes(), &out); err != nil {
+		t.Fatal(err)
+	}
+	if len(out) != 2 {
+		t.Fatalf("expected 2 items, got %v", out)
+	}
+}
+
+func TestWriteErrorLogsClientError(t *testing.T) {
+	var buf bytes.Buffer
+	prev := slog.Default()
+	slog.SetDefault(slog.New(slog.NewJSONHandler(&buf, &slog.HandlerOptions{Level: slog.LevelWarn})))
+	defer slog.SetDefault(prev)
+
+	req := httptest.NewRequest(http.MethodPost, "/api/settings/notify/test", nil)
+	rec := httptest.NewRecorder()
+	writeError(req, rec, http.StatusBadRequest, "请填写 SMTP 主机")
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d", rec.Code)
+	}
+	if !bytes.Contains(buf.Bytes(), []byte("请填写 SMTP 主机")) {
+		t.Fatalf("expected log message, got %s", buf.String())
+	}
+	if !bytes.Contains(buf.Bytes(), []byte("/api/settings/notify/test")) {
+		t.Fatalf("expected log path, got %s", buf.String())
+	}
+}