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_simulation_integration_test.go

@@ -134,13 +134,14 @@ WHERE username = $1`, username); err != nil {
 					ResponseDurationMS int64          `json:"responseDurationMs"`
 				} `json:"task"`
 			}
-			doJSON(
+			doJSONWithHeaders(
 				t,
 				server.URL,
 				http.MethodPost,
 				"/api/v1/videos/generations",
 				apiKeyResponse.Secret,
 				request,
+				map[string]string{"X-Async": "true"},
 				http.StatusAccepted,
 				&response,
 			)