feat(log): replace standard logger with zerolog

- Integrate `rs/zerolog` for structured and leveled logging
- Add `EZ_LOG_LEVEL` environment variable support (default: info)
- Configure console output with timestamps and service fields
- Migrate `main.go` and `LogWriter` to use the new logger instance
- Update README with logging configuration and design details

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/bytedance/sonic v1.14.0
 	github.com/gin-gonic/gin v1.11.0
 	github.com/redis/go-redis/v9 v9.17.2
+	github.com/rs/zerolog v1.34.0
 	github.com/swaggo/files v1.0.1
 	github.com/swaggo/gin-swagger v1.6.1
 	github.com/swaggo/swag v1.16.6
@@ -47,6 +48,7 @@ require (
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect