fix(test): 修复测试和添加数据库迁移

测试修复：
- 修复集成测试中的重复键冲突问题
- 移除 JSON 中多余的尾随逗号
- 新增 inprocess_transport_test.go
- 更新 haiku 模型映射测试用例

数据库迁移：
- 026: 运营指标聚合表
- 027: 使用量与计费一致性约束

backend/internal/repository/inprocess_transport_test.go

@@ -0,0 +1,63 @@
+package repository
+
+import (
+	"bytes"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+)
+
+type roundTripFunc func(*http.Request) (*http.Response, error)
+
+func (f roundTripFunc) RoundTrip(r *http.Request) (*http.Response, error) { return f(r) }
+
+// newInProcessTransport adapts an http.HandlerFunc into an http.RoundTripper without opening sockets.
+// It captures the request body (if any) and then rewinds it before invoking the handler.
+func newInProcessTransport(handler http.HandlerFunc, capture func(r *http.Request, body []byte)) http.RoundTripper {
+	return roundTripFunc(func(r *http.Request) (*http.Response, error) {
+		var body []byte
+		if r.Body != nil {
+			body, _ = io.ReadAll(r.Body)
+			_ = r.Body.Close()
+			r.Body = io.NopCloser(bytes.NewReader(body))
+		}
+		if capture != nil {
+			capture(r, body)
+		}
+
+		rec := httptest.NewRecorder()
+		handler(rec, r)
+		return rec.Result(), nil
+	})
+}
+
+var (
+	canListenOnce sync.Once
+	canListen     bool
+	canListenErr  error
+)
+
+func localListenerAvailable() bool {
+	canListenOnce.Do(func() {
+		ln, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			canListenErr = err
+			canListen = false
+			return
+		}
+		_ = ln.Close()
+		canListen = true
+	})
+	return canListen
+}
+
+func newLocalTestServer(tb testing.TB, handler http.Handler) *httptest.Server {
+	tb.Helper()
+	if !localListenerAvailable() {
+		tb.Skipf("local listeners are not permitted in this environment: %v", canListenErr)
+	}
+	return httptest.NewServer(handler)
+}