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/router/router.go

@@ -13,6 +13,7 @@ import (
 	"github.com/treytartt/casera-api/internal/handlers"
 	"github.com/treytartt/casera-api/internal/i18n"
 	"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"
@@ -23,13 +24,14 @@ const Version = "2.0.0"
 
 // Dependencies holds all dependencies needed by the router
 type Dependencies struct {
-	DB             *gorm.DB
-	Cache          *services.CacheService
-	Config         *config.Config
-	EmailService   *services.EmailService
-	PDFService     *services.PDFService
-	PushClient     *push.Client // Direct APNs/FCM client
-	StorageService *services.StorageService
+	DB                *gorm.DB
+	Cache             *services.CacheService
+	Config            *config.Config
+	EmailService      *services.EmailService
+	PDFService        *services.PDFService
+	PushClient        *push.Client // Direct APNs/FCM client
+	StorageService    *services.StorageService
+	MonitoringService *monitoring.Service
 }
 
 // SetupRouter creates and configures the Gin router
@@ -51,6 +53,13 @@ func SetupRouter(deps *Dependencies) *gin.Engine {
 	r.Use(corsMiddleware(cfg))
 	r.Use(i18n.Middleware())
 
+	// Monitoring metrics middleware (if monitoring is enabled)
+	if deps.MonitoringService != nil {
+		if metricsMiddleware := deps.MonitoringService.MetricsMiddleware(); metricsMiddleware != nil {
+			r.Use(metricsMiddleware.(gin.HandlerFunc))
+		}
+	}
+
 	// Serve landing page static files (if static directory is configured)
 	staticDir := cfg.Server.StaticDir
 	if staticDir != "" {
@@ -137,11 +146,17 @@ func SetupRouter(deps *Dependencies) *gin.Engine {
 		mediaHandler = handlers.NewMediaHandler(documentRepo, taskRepo, residenceRepo, deps.StorageService)
 	}
 
-	// Set up admin routes (separate auth system)
+	// Set up admin routes with monitoring handler (if available)
+	var monitoringHandler *monitoring.Handler
+	if deps.MonitoringService != nil {
+		monitoringHandler = deps.MonitoringService.Handler()
+	}
+
 	adminDeps := &admin.Dependencies{
 		EmailService:      deps.EmailService,
 		PushClient:        deps.PushClient,
 		OnboardingService: onboardingService,
+		MonitoringHandler: monitoringHandler,
 	}
 	admin.SetupRoutes(r, deps.DB, cfg, adminDeps)