refactor(log): migrate from zerolog to structured slog with bridge

- Replace direct zerolog usage with standard library `log/slog` in business code
- Add `internal/logging` package with zerolog bridge handler for structured output
- Create `internal/jsoncodec` package to centralize JSON encoding/decoding using Sonic
- Update all services and main entry point to use new logging interface
- Maintain backward compatibility with existing zerolog console output
- Remove custom logger setup in favor of structured logging bridge

internal/service/logger.go

@@ -2,10 +2,10 @@ package service
 
 import (
 	"context"
+	"log/slog"
 	"time"
 
 	"github.com/ez-api/ez-api/internal/model"
-	"github.com/rs/zerolog/log"
 	"gorm.io/gorm"
 )
 
@@ -47,7 +47,7 @@ func (w *LogWriter) Start(ctx context.Context) {
 				return
 			}
 			if err := w.db.Create(&buf).Error; err != nil {
-				log.Error().Err(err).Msg("log batch insert failed")
+				slog.Default().Error("log batch insert failed", "err", err)
 			}
 			buf = buf[:0]
 		}