feat(logging): introduce centralized logging with custom format and Gin integration

- Implemented a global logger with structured formatting for consistent log output.
- Added support for rotating log files using Lumberjack.
- Integrated new logging functionality with Gin HTTP server for unified log handling.
- Replaced direct `log.Info` calls with `fmt.Printf` in non-critical paths to simplify core functionality.

internal/logging/global_logger.go

@@ -0,0 +1,117 @@
+package logging
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"github.com/gin-gonic/gin"
+	log "github.com/sirupsen/logrus"
+	"gopkg.in/natefinch/lumberjack.v2"
+)
+
+var (
+	setupOnce      sync.Once
+	writerMu       sync.Mutex
+	logWriter      *lumberjack.Logger
+	ginInfoWriter  *io.PipeWriter
+	ginErrorWriter *io.PipeWriter
+)
+
+// LogFormatter defines a custom log format for logrus.
+// This formatter adds timestamp, level, and source location to each log entry.
+type LogFormatter struct{}
+
+// Format renders a single log entry with custom formatting.
+func (m *LogFormatter) Format(entry *log.Entry) ([]byte, error) {
+	var buffer *bytes.Buffer
+	if entry.Buffer != nil {
+		buffer = entry.Buffer
+	} else {
+		buffer = &bytes.Buffer{}
+	}
+
+	timestamp := entry.Time.Format("2006-01-02 15:04:05")
+	message := strings.TrimRight(entry.Message, "\r\n")
+	formatted := fmt.Sprintf("[%s] [%s] [%s:%d] %s\n", timestamp, entry.Level, filepath.Base(entry.Caller.File), entry.Caller.Line, message)
+	buffer.WriteString(formatted)
+
+	return buffer.Bytes(), nil
+}
+
+// SetupBaseLogger configures the shared logrus instance and Gin writers.
+// It is safe to call multiple times; initialization happens only once.
+func SetupBaseLogger() {
+	setupOnce.Do(func() {
+		log.SetOutput(os.Stdout)
+		log.SetReportCaller(true)
+		log.SetFormatter(&LogFormatter{})
+
+		ginInfoWriter = log.StandardLogger().Writer()
+		gin.DefaultWriter = ginInfoWriter
+		ginErrorWriter = log.StandardLogger().WriterLevel(log.ErrorLevel)
+		gin.DefaultErrorWriter = ginErrorWriter
+		gin.DebugPrintFunc = func(format string, values ...interface{}) {
+			format = strings.TrimRight(format, "\r\n")
+			log.StandardLogger().Infof(format, values...)
+		}
+
+		log.RegisterExitHandler(closeLogOutputs)
+	})
+}
+
+// ConfigureLogOutput switches the global log destination between rotating files and stdout.
+func ConfigureLogOutput(loggingToFile bool) error {
+	SetupBaseLogger()
+
+	writerMu.Lock()
+	defer writerMu.Unlock()
+
+	if loggingToFile {
+		const logDir = "logs"
+		if err := os.MkdirAll(logDir, 0o755); err != nil {
+			return fmt.Errorf("logging: failed to create log directory: %w", err)
+		}
+		if logWriter != nil {
+			_ = logWriter.Close()
+		}
+		logWriter = &lumberjack.Logger{
+			Filename:   filepath.Join(logDir, "main.log"),
+			MaxSize:    10,
+			MaxBackups: 0,
+			MaxAge:     0,
+			Compress:   false,
+		}
+		log.SetOutput(logWriter)
+		return nil
+	}
+
+	if logWriter != nil {
+		_ = logWriter.Close()
+		logWriter = nil
+	}
+	log.SetOutput(os.Stdout)
+	return nil
+}
+
+func closeLogOutputs() {
+	writerMu.Lock()
+	defer writerMu.Unlock()
+
+	if logWriter != nil {
+		_ = logWriter.Close()
+		logWriter = nil
+	}
+	if ginInfoWriter != nil {
+		_ = ginInfoWriter.Close()
+		ginInfoWriter = nil
+	}
+	if ginErrorWriter != nil {
+		_ = ginErrorWriter.Close()
+		ginErrorWriter = nil
+	}
+}