Add real-time log monitoring and system stats dashboard

Implements a comprehensive monitoring system for the admin interface:

Backend:
- New monitoring package with Redis ring buffer for log storage
- Zerolog MultiWriter to capture logs to Redis
- System stats collection (CPU, memory, disk, goroutines, GC)
- HTTP metrics middleware (request counts, latency, error rates)
- Asynq queue stats for worker process
- WebSocket endpoint for real-time log streaming
- Admin auth middleware now accepts token in query params (for WebSocket)

Frontend:
- New monitoring page with tabs (Overview, Logs, API Stats, Worker Stats)
- Real-time log viewer with level filtering and search
- System stats cards showing CPU, memory, goroutines, uptime
- HTTP endpoint statistics table
- Asynq queue depth visualization
- Enable/disable monitoring toggle in settings

Memory safeguards:
- Max 200 unique endpoints tracked
- Hourly stats reset to prevent unbounded growth
- Max 1000 log entries in ring buffer
- Max 1000 latency samples for P95 calculation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/admin/handlers/settings_handler.go

@@ -29,6 +29,7 @@ func NewAdminSettingsHandler(db *gorm.DB) *AdminSettingsHandler {
 // SettingsResponse represents the settings response
 type SettingsResponse struct {
 	EnableLimitations bool `json:"enable_limitations"`
+	EnableMonitoring  bool `json:"enable_monitoring"`
 }
 
 // GetSettings handles GET /api/admin/settings
@@ -37,7 +38,7 @@ func (h *AdminSettingsHandler) GetSettings(c *gin.Context) {
 	if err := h.db.First(&settings, 1).Error; err != nil {
 		if err == gorm.ErrRecordNotFound {
 			// Create default settings
-			settings = models.SubscriptionSettings{ID: 1, EnableLimitations: false}
+			settings = models.SubscriptionSettings{ID: 1, EnableLimitations: false, EnableMonitoring: true}
 			h.db.Create(&settings)
 		} else {
 			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to fetch settings"})
@@ -47,12 +48,14 @@ func (h *AdminSettingsHandler) GetSettings(c *gin.Context) {
 
 	c.JSON(http.StatusOK, SettingsResponse{
 		EnableLimitations: settings.EnableLimitations,
+		EnableMonitoring:  settings.EnableMonitoring,
 	})
 }
 
 // UpdateSettingsRequest represents the update request
 type UpdateSettingsRequest struct {
 	EnableLimitations *bool `json:"enable_limitations"`
+	EnableMonitoring  *bool `json:"enable_monitoring"`
 }
 
 // UpdateSettings handles PUT /api/admin/settings
@@ -66,7 +69,7 @@ func (h *AdminSettingsHandler) UpdateSettings(c *gin.Context) {
 	var settings models.SubscriptionSettings
 	if err := h.db.First(&settings, 1).Error; err != nil {
 		if err == gorm.ErrRecordNotFound {
-			settings = models.SubscriptionSettings{ID: 1}
+			settings = models.SubscriptionSettings{ID: 1, EnableMonitoring: true}
 		} else {
 			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to fetch settings"})
 			return
@@ -77,6 +80,10 @@ func (h *AdminSettingsHandler) UpdateSettings(c *gin.Context) {
 		settings.EnableLimitations = *req.EnableLimitations
 	}
 
+	if req.EnableMonitoring != nil {
+		settings.EnableMonitoring = *req.EnableMonitoring
+	}
+
 	if err := h.db.Save(&settings).Error; err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update settings"})
 		return
@@ -84,6 +91,7 @@ func (h *AdminSettingsHandler) UpdateSettings(c *gin.Context) {
 
 	c.JSON(http.StatusOK, SettingsResponse{
 		EnableLimitations: settings.EnableLimitations,
+		EnableMonitoring:  settings.EnableMonitoring,
 	})
 }
 

internal/admin/routes.go

@@ -12,6 +12,7 @@ import (
 	"github.com/treytartt/casera-api/internal/admin/handlers"
 	"github.com/treytartt/casera-api/internal/config"
 	"github.com/treytartt/casera-api/internal/middleware"
+	"github.com/treytartt/casera-api/internal/monitoring"
 	"github.com/treytartt/casera-api/internal/push"
 	"github.com/treytartt/casera-api/internal/repositories"
 	"github.com/treytartt/casera-api/internal/services"
@@ -22,6 +23,7 @@ type Dependencies struct {
 	EmailService        *services.EmailService
 	PushClient          *push.Client
 	OnboardingService   *services.OnboardingEmailService
+	MonitoringHandler   *monitoring.Handler
 }
 
 // SetupRoutes configures all admin routes
@@ -424,6 +426,17 @@ func SetupRoutes(router *gin.Engine, db *gorm.DB, cfg *config.Config, deps *Depe
 				onboardingEmails.GET("/:id", onboardingHandler.Get)
 				onboardingEmails.DELETE("/:id", onboardingHandler.Delete)
 			}
+
+			// System monitoring (logs, stats, websocket)
+			if deps != nil && deps.MonitoringHandler != nil {
+				monitoringGroup := protected.Group("/monitoring")
+				{
+					monitoringGroup.GET("/logs", deps.MonitoringHandler.GetLogs)
+					monitoringGroup.GET("/stats", deps.MonitoringHandler.GetStats)
+					monitoringGroup.DELETE("/logs", deps.MonitoringHandler.ClearLogs)
+					monitoringGroup.GET("/ws", deps.MonitoringHandler.WebSocket)
+				}
+			}
 		}
 	}