feat: add Sora admin page and integrate DB/Redis Prometheus metrics

- Create SoraAdminView with overview, user stats, and generations tabs
- Add /admin/sora route for Sora management
- Add i18n support (zh/en) for Sora admin page
- Extract Prometheus metrics to prommetrics package to avoid import cycles
- Integrate SetDBConnections/SetRedisConnections in OpsMetricsCollector

backend/internal/server/routes/common.go

@@ -2,12 +2,11 @@ package routes
 
 import (
 	"net/http"
-	"strconv"
 	"sync"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/prommetrics"
 	"github.com/gin-gonic/gin"
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
@@ -20,125 +19,8 @@ type HealthChecker interface {
 var (
 	healthChecker     HealthChecker
 	healthCheckerOnce sync.Once
-
-	// Prometheus metrics
-	prometheusRegistry = prometheus.NewRegistry()
-
-	// Custom metrics
-	httpRequestsTotal = prometheus.NewCounterVec(
-		prometheus.CounterOpts{
-			Name: "sub2api_http_requests_total",
-			Help: "Total number of HTTP requests",
-		},
-		[]string{"method", "path", "status"},
-	)
-
-	httpRequestDuration = prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "sub2api_http_request_duration_seconds",
-			Help:    "HTTP request duration in seconds",
-			Buckets: prometheus.DefBuckets,
-		},
-		[]string{"method", "path"},
-	)
-
-	dbConnectionsActive = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_db_connections_active",
-			Help: "Number of active database connections",
-		},
-	)
-
-	dbConnectionsIdle = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_db_connections_idle",
-			Help: "Number of idle database connections",
-		},
-	)
-
-	redisConnectionsTotal = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_redis_connections_total",
-			Help: "Total number of Redis connections",
-		},
-	)
-
-	redisConnectionsIdle = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_redis_connections_idle",
-			Help: "Number of idle Redis connections",
-		},
-	)
-
-	accountActiveTotal = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_accounts_active_total",
-			Help: "Total number of active accounts",
-		},
-	)
-
-	requestQueueDepth = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_request_queue_depth",
-			Help: "Current request queue depth",
-		},
-	)
-
-	opsHealthScore = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_ops_health_score",
-			Help: "Overall system health score (0-100)",
-		},
-	)
-
-	errorRate = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_error_rate",
-			Help: "Current error rate",
-		},
-	)
-
-	successRate = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_success_rate",
-			Help: "Current success rate",
-		},
-	)
-
-	qps = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_qps",
-			Help: "Queries per second",
-		},
-	)
-
-	tps = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Name: "sub2api_tps",
-			Help: "Tokens per second",
-		},
-	)
 )
 
-func init() {
-	// Register custom metrics
-	prometheusRegistry.MustRegister(
-		httpRequestsTotal,
-		httpRequestDuration,
-		dbConnectionsActive,
-		dbConnectionsIdle,
-		redisConnectionsTotal,
-		redisConnectionsIdle,
-		accountActiveTotal,
-		requestQueueDepth,
-		opsHealthScore,
-		errorRate,
-		successRate,
-		qps,
-		tps,
-	)
-}
-
 // SetHealthChecker sets the health checker instance (called during app initialization)
 func SetHealthChecker(checker HealthChecker) {
 	healthCheckerOnce.Do(func() {
@@ -157,8 +39,8 @@ func RegisterCommonRoutes(r *gin.Engine) {
 	// Liveness check - for Kubernetes liveness probe
 	r.GET("/live", livenessHandler)
 
-	// Prometheus metrics endpoint
-	r.GET("/metrics", gin.WrapH(promhttp.HandlerFor(prometheusRegistry, promhttp.HandlerOpts{})))
+	// Prometheus metrics endpoint - use the shared registry from prommetrics package
+	r.GET("/metrics", gin.WrapH(promhttp.HandlerFor(prommetrics.Registry, promhttp.HandlerOpts{})))
 
 	// Claude Code telemetry logs (ignore, return 200 directly)
 	r.POST("/api/event_logging/batch", func(c *gin.Context) {
@@ -275,57 +157,54 @@ func livenessHandler(c *gin.Context) {
 	})
 }
 
-// Prometheus metric update functions
+// Prometheus metric update functions - delegate to prommetrics package
 
 // RecordHTTPRequest records an HTTP request for Prometheus metrics
 func RecordHTTPRequest(method, path string, statusCode int, duration time.Duration) {
-	httpRequestsTotal.WithLabelValues(method, path, strconv.Itoa(statusCode)).Inc()
-	httpRequestDuration.WithLabelValues(method, path).Observe(duration.Seconds())
+	prommetrics.RecordHTTPRequest(method, path, statusCode, duration)
 }
 
 // SetDBConnections sets database connection metrics
 func SetDBConnections(active, idle int) {
-	dbConnectionsActive.Set(float64(active))
-	dbConnectionsIdle.Set(float64(idle))
+	prommetrics.SetDBConnections(active, idle)
 }
 
 // SetRedisConnections sets Redis connection metrics
 func SetRedisConnections(total, idle int) {
-	redisConnectionsTotal.Set(float64(total))
-	redisConnectionsIdle.Set(float64(idle))
+	prommetrics.SetRedisConnections(total, idle)
 }
 
 // SetActiveAccounts sets the active accounts count
 func SetActiveAccounts(count int) {
-	accountActiveTotal.Set(float64(count))
+	prommetrics.SetActiveAccounts(count)
 }
 
 // SetRequestQueueDepth sets the request queue depth
 func SetRequestQueueDepth(depth int) {
-	requestQueueDepth.Set(float64(depth))
+	prommetrics.SetRequestQueueDepth(depth)
 }
 
 // SetOpsHealthScore sets the overall health score
 func SetOpsHealthScore(score int) {
-	opsHealthScore.Set(float64(score))
+	prommetrics.SetOpsHealthScore(score)
 }
 
 // SetErrorRate sets the error rate
 func SetErrorRate(rate float64) {
-	errorRate.Set(rate)
+	prommetrics.SetErrorRate(rate)
 }
 
 // SetSuccessRate sets the success rate
 func SetSuccessRate(rate float64) {
-	successRate.Set(rate)
+	prommetrics.SetSuccessRate(rate)
 }
 
 // SetQPS sets queries per second
 func SetQPS(value float64) {
-	qps.Set(value)
+	prommetrics.SetQPS(value)
 }
 
 // SetTPS sets tokens per second
 func SetTPS(value float64) {
-	tps.Set(value)
+	prommetrics.SetTPS(value)
 }