feat(handler): 实现运维监控 API 处理器和中间件

- 新增 ops 错误日志记录器（ops_error_logger.go）
- 新增 ops 主处理器（ops_handler.go）
- 新增告警管理处理器（ops_alerts_handler.go）
- 新增仪表板处理器（ops_dashboard_handler.go）
- 新增实时监控处理器（ops_realtime_handler.go）
- 新增配置管理处理器（ops_settings_handler.go）
- 新增 WebSocket 处理器（ops_ws_handler.go）
- 扩展设置 DTO 支持 ops 配置
- 新增客户端请求 ID 中间件（client_request_id.go）
- 新增 WebSocket 查询令牌认证中间件（ws_query_token_auth.go）
- 更新管理员认证中间件支持 ops 路由
- 注册 handler 依赖注入

backend/internal/handler/admin/ops_realtime_handler.go

@@ -0,0 +1,120 @@
+package admin
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/gin-gonic/gin"
+)
+
+// GetConcurrencyStats returns real-time concurrency usage aggregated by platform/group/account.
+// GET /api/v1/admin/ops/concurrency
+func (h *OpsHandler) GetConcurrencyStats(c *gin.Context) {
+	if h.opsService == nil {
+		response.Error(c, http.StatusServiceUnavailable, "Ops service not available")
+		return
+	}
+	if err := h.opsService.RequireMonitoringEnabled(c.Request.Context()); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	if !h.opsService.IsRealtimeMonitoringEnabled(c.Request.Context()) {
+		response.Success(c, gin.H{
+			"enabled":   false,
+			"platform":  map[string]*service.PlatformConcurrencyInfo{},
+			"group":     map[int64]*service.GroupConcurrencyInfo{},
+			"account":   map[int64]*service.AccountConcurrencyInfo{},
+			"timestamp": time.Now().UTC(),
+		})
+		return
+	}
+
+	platformFilter := strings.TrimSpace(c.Query("platform"))
+	var groupID *int64
+	if v := strings.TrimSpace(c.Query("group_id")); v != "" {
+		id, err := strconv.ParseInt(v, 10, 64)
+		if err != nil || id <= 0 {
+			response.BadRequest(c, "Invalid group_id")
+			return
+		}
+		groupID = &id
+	}
+
+	platform, group, account, collectedAt, err := h.opsService.GetConcurrencyStats(c.Request.Context(), platformFilter, groupID)
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	payload := gin.H{
+		"enabled":  true,
+		"platform": platform,
+		"group":    group,
+		"account":  account,
+	}
+	if collectedAt != nil {
+		payload["timestamp"] = collectedAt.UTC()
+	}
+	response.Success(c, payload)
+}
+
+// GetAccountAvailability returns account availability statistics.
+// GET /api/v1/admin/ops/account-availability
+//
+// Query params:
+// - platform: optional
+// - group_id: optional
+func (h *OpsHandler) GetAccountAvailability(c *gin.Context) {
+	if h.opsService == nil {
+		response.Error(c, http.StatusServiceUnavailable, "Ops service not available")
+		return
+	}
+	if err := h.opsService.RequireMonitoringEnabled(c.Request.Context()); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	if !h.opsService.IsRealtimeMonitoringEnabled(c.Request.Context()) {
+		response.Success(c, gin.H{
+			"enabled":   false,
+			"platform":  map[string]*service.PlatformAvailability{},
+			"group":     map[int64]*service.GroupAvailability{},
+			"account":   map[int64]*service.AccountAvailability{},
+			"timestamp": time.Now().UTC(),
+		})
+		return
+	}
+
+	platform := strings.TrimSpace(c.Query("platform"))
+	var groupID *int64
+	if v := strings.TrimSpace(c.Query("group_id")); v != "" {
+		id, err := strconv.ParseInt(v, 10, 64)
+		if err != nil || id <= 0 {
+			response.BadRequest(c, "Invalid group_id")
+			return
+		}
+		groupID = &id
+	}
+
+	platformStats, groupStats, accountStats, collectedAt, err := h.opsService.GetAccountAvailabilityStats(c.Request.Context(), platform, groupID)
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	payload := gin.H{
+		"enabled":  true,
+		"platform": platformStats,
+		"group":    groupStats,
+		"account":  accountStats,
+	}
+	if collectedAt != nil {
+		payload["timestamp"] = collectedAt.UTC()
+	}
+	response.Success(c, payload)
+}