feat(api): 统一公开接口为 /api/v1 前缀

将通用生成、Gemini、可灵、火山、健康检查与 OpenAPI 的推荐入口统一到 /api/v1，并保留历史路径作为兼容别名。同步更新代理配置、接入文档、接口清单和前缀回归测试。\n\n验证：go vet ./...；go test ./...；pnpm openapi；pnpm lint；pnpm test；pnpm build；公开 OpenAPI 71 个方法与接口清单机器比对一致。

apps/api/internal/httpapi/keling_compat_integration_test.go

@@ -145,7 +145,7 @@ func TestKelingOmniCompatibleHTTPFlow(t *testing.T) {
 	_, secondAPIKey := createKelingCompatIntegrationUser(t, ctx, db, gateway.URL, "second", suffix, false)
 
 	var created KelingCompatibleEnvelope
-	doJSON(t, gateway.URL, http.MethodPost, "/v1/videos/omni-video", firstAPIKey, map[string]any{
+	doJSON(t, gateway.URL, http.MethodPost, "/api/v1/videos/omni-video", firstAPIKey, map[string]any{
 		"model_name":       "kling-video-o1",
 		"prompt":           "A clean product reveal",
 		"mode":             "std",
@@ -162,7 +162,7 @@ func TestKelingOmniCompatibleHTTPFlow(t *testing.T) {
 	taskID := stringFromKelingCompat(createdData["task_id"])
 
 	var hidden KelingCompatibleEnvelope
-	doJSON(t, gateway.URL, http.MethodGet, "/v1/videos/omni-video/"+taskID, secondAPIKey, nil, http.StatusNotFound, &hidden)
+	doJSON(t, gateway.URL, http.MethodGet, "/api/v1/videos/omni-video/"+taskID, secondAPIKey, nil, http.StatusNotFound, &hidden)
 	if hidden.Code != 1203 {
 		t.Fatalf("cross-user task must be hidden: %+v", hidden)
 	}
@@ -278,7 +278,7 @@ func waitForKelingCompatTask(t *testing.T, baseURL string, apiKey string, taskID
 	deadline := time.Now().Add(timeout)
 	for time.Now().Before(deadline) {
 		var response KelingCompatibleEnvelope
-		doJSON(t, baseURL, http.MethodGet, "/v1/videos/omni-video/"+taskID, apiKey, nil, http.StatusOK, &response)
+		doJSON(t, baseURL, http.MethodGet, "/api/v1/videos/omni-video/"+taskID, apiKey, nil, http.StatusOK, &response)
 		data, _ := response.Data.(map[string]any)
 		switch data["task_status"] {
 		case "succeed":