refactor(cron): migrate cron jobs to foundation scheduler

Replace custom goroutine-based scheduling in cron jobs with centralized
foundation scheduler. Each cron job now exposes a RunOnce method called
by the scheduler instead of managing its own ticker loop.

Changes:
- Remove interval/enabled config from cron job structs
- Convert Start() methods to RunOnce() for all cron jobs
- Add scheduler setup in main.go with configurable intervals
- Update foundation dependency to v0.6.0 for scheduler support
- Update tests to validate RunOnce nil-safety

cmd/server/main.go

@@ -23,6 +23,7 @@ import (
 	"github.com/ez-api/ez-api/internal/model"
 	"github.com/ez-api/ez-api/internal/service"
 	"github.com/ez-api/foundation/logging"
+	"github.com/ez-api/foundation/scheduler"
 	"github.com/gin-gonic/gin"
 	"github.com/redis/go-redis/v9"
 	swaggerFiles "github.com/swaggo/files"
@@ -186,33 +187,29 @@ func main() {
 	logCtx, cancelLogs := context.WithCancel(context.Background())
 	defer cancelLogs()
 	logWriter.Start(logCtx)
-	quotaResetter := cron.NewQuotaResetter(db, syncService, time.Duration(cfg.Quota.ResetIntervalSeconds)*time.Second)
-	quotaCtx, cancelQuota := context.WithCancel(context.Background())
-	defer cancelQuota()
-	go quotaResetter.Start(quotaCtx)
-	logCleaner := cron.NewLogCleaner(logDB, rdb, cfg.Log.RetentionDays, int64(cfg.Log.MaxRecords), time.Hour, logPartitioner)
-	cleanerCtx, cancelCleaner := context.WithCancel(context.Background())
-	defer cancelCleaner()
-	go logCleaner.Start(cleanerCtx)
+
+	// Initialize cron jobs
+	quotaResetter := cron.NewQuotaResetter(db, syncService)
+	logCleaner := cron.NewLogCleaner(logDB, rdb, cfg.Log.RetentionDays, int64(cfg.Log.MaxRecords), logPartitioner)
 	tokenRefresher := cron.NewTokenRefresher(
 		db,
 		rdb,
 		syncService,
-		time.Duration(cfg.TokenRefresh.IntervalSeconds)*time.Second,
 		time.Duration(cfg.TokenRefresh.RefreshSkewSeconds)*time.Second,
 		cfg.TokenRefresh.BatchSize,
 		cfg.TokenRefresh.MaxRetries,
 	)
-	tokenCtx, cancelToken := context.WithCancel(context.Background())
-	defer cancelToken()
-	go tokenRefresher.Start(tokenCtx)
-
-	// Alert Detector
 	alertDetectorConfig := cron.DefaultAlertDetectorConfig()
 	alertDetector := cron.NewAlertDetector(db, logDB, rdb, service.NewStatsService(rdb), alertDetectorConfig, logger)
-	alertDetectorCtx, cancelAlertDetector := context.WithCancel(context.Background())
-	defer cancelAlertDetector()
-	go alertDetector.Start(alertDetectorCtx)
+
+	// Setup scheduler
+	sched := scheduler.New(scheduler.WithLogger(logger), scheduler.WithSkipIfRunning())
+	sched.Every("quota-reset", time.Duration(cfg.Quota.ResetIntervalSeconds)*time.Second, quotaResetter.RunOnce)
+	sched.Every("log-cleanup", time.Hour, logCleaner.RunOnce)
+	sched.Every("token-refresh", time.Duration(cfg.TokenRefresh.IntervalSeconds)*time.Second, tokenRefresher.RunOnce)
+	sched.Every("alert-detection", time.Minute, alertDetector.RunOnce)
+	sched.Start()
+	defer sched.Stop()
 
 	adminService, err := service.NewAdminService()
 	if err != nil {