Merge tag 'v0.1.79' into develop

增强错误处理与重试机制，新增 MODEL_CAPACITY_EXHAUSTED 同账号固定间隔重试、瞬态错误同账号重试优先于故障转移，并大幅优化错误匹配性能。

- MODEL_CAPACITY_EXHAUSTED (503) 使用固定 1s 间隔重试最多 60 次，不切换账号
- 瞬态错误（Google 400、空流响应）同账号重试 2 次后再触发故障转移
- 空流响应触发 failover 自动换号重试，不再直接返回 502
- Google "Invalid project resource name" 400 错误触发 failover 并临时封禁账号 1 小时
- 错误透传规则新增 skip_monitoring 选项，匹配的错误不记录到运维监控日志
- Antigravity 转发支持 daily/prod 单 URL 切换

- 错误匹配性能优化：延迟/限制 body ToLower，预计算规则关键词和平台集合
- MODEL_CAPACITY_EXHAUSTED 全局去重，避免并发请求重复重试
- 503 重试 body 读取限制从 2MB 降至 8KB
- time.After 替换为 time.NewTimer，防止 context 取消时 timer 泄漏
- 临时封禁冷却时间从 30 分钟缩短至 1 分钟（同账号重试耗尽后）

- 修复错误透传规则 skip_monitoring 未生效的问题
- 修复 CI 检查失败（gofmt、errcheck、staticcheck）

# Conflicts:
#	backend/internal/service/error_passthrough_runtime_test.go

backend/internal/handler/gateway_handler.go

@@ -896,6 +896,10 @@ func (h *GatewayHandler) handleFailoverExhausted(c *gin.Context, failoverErr *se
 				msg = *rule.CustomMessage
 			}
 
+			if rule.SkipMonitoring {
+				c.Set(service.OpsSkipPassthroughKey, true)
+			}
+
 			h.handleStreamingAwareError(c, respCode, "upstream_error", msg, streamStarted)
 			return
 		}

backend/internal/handler/gemini_v1beta_handler.go

@@ -542,6 +542,10 @@ func (h *GatewayHandler) handleGeminiFailoverExhausted(c *gin.Context, failoverE
 				msg = *rule.CustomMessage
 			}
 
+			if rule.SkipMonitoring {
+				c.Set(service.OpsSkipPassthroughKey, true)
+			}
+
 			googleError(c, respCode, msg)
 			return
 		}

backend/internal/handler/openai_gateway_handler.go

@@ -354,6 +354,10 @@ func (h *OpenAIGatewayHandler) handleFailoverExhausted(c *gin.Context, failoverE
 				msg = *rule.CustomMessage
 			}
 
+			if rule.SkipMonitoring {
+				c.Set(service.OpsSkipPassthroughKey, true)
+			}
+
 			h.handleStreamingAwareError(c, respCode, "upstream_error", msg, streamStarted)
 			return
 		}

backend/internal/handler/ops_error_logger.go

@@ -537,6 +537,13 @@ func OpsErrorLoggerMiddleware(ops *service.OpsService) gin.HandlerFunc {
 			// Store request headers/body only when an upstream error occurred to keep overhead minimal.
 			entry.RequestHeadersJSON = extractOpsRetryRequestHeaders(c)
 
+			// Skip logging if a passthrough rule with skip_monitoring=true matched.
+			if v, ok := c.Get(service.OpsSkipPassthroughKey); ok {
+				if skip, _ := v.(bool); skip {
+					return
+				}
+			}
+
 			enqueueOpsErrorLog(ops, entry, requestBody)
 			return
 		}