refactor(log): migrate from log to log/slog for structured logging

Replace all usages of the standard log package with log/slog across
backend and swift worker. Configure Echo's request logger to emit
structured log attributes via slog instead of the default format.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 28 insertions, 4 deletions

diff --git a/worker/swift/main.go b/worker/swift/main.go
index d3d14db..2761602 100644
--- a/worker/swift/main.go
+++ b/worker/swift/main.go
@@ -1,8 +1,10 @@
 package main
 
 import (
-	"log"
+	"context"
+	"log/slog"
 	"net/http"
+	"os"
 
 	"github.com/labstack/echo/v4"
 	"github.com/labstack/echo/v4/middleware"
@@ -10,17 +12,39 @@ import (
 
 func main() {
 	if err := prepareDirectories(); err != nil {
-		log.Fatal(err)
+		slog.Error("failed to prepare directories", "error", err)
+		os.Exit(1)
 	}
 
 	e := echo.New()
 
-	e.Use(middleware.RequestLogger())
+	e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
+		LogStatus:   true,
+		LogURI:      true,
+		LogMethod:   true,
+		LogLatency:  true,
+		LogError:    true,
+		HandleError: true,
+		LogValuesFunc: func(_ echo.Context, v middleware.RequestLoggerValues) error {
+			attrs := []slog.Attr{
+				slog.String("method", v.Method),
+				slog.String("uri", v.URI),
+				slog.Int("status", v.Status),
+				slog.Duration("latency", v.Latency),
+			}
+			if v.Error != nil {
+				attrs = append(attrs, slog.String("error", v.Error.Error()))
+			}
+			slog.LogAttrs(context.Background(), slog.LevelInfo, "request", attrs...)
+			return nil
+		},
+	}))
 	e.Use(middleware.Recover())
 
 	e.POST("/exec", handleExec)
 
 	if err := e.Start(":80"); err != http.ErrServerClosed {
-		log.Fatal(err)
+		slog.Error("failed to start server", "error", err)
+		os.Exit(1)
 	}
 }