refactor: rename internal/log to internal/logging to avoid stdlib

shadowing

- refactor: rename `internal/log` → `internal/logging`, package `log` →
  `logging`
- refactor: update imports in `cmd/serve.go` and
  `internal/middleware/requestid.go`

internal/middleware/requestid.go

@@ -4,7 +4,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/google/uuid"
 
-	mygolog "github.com/dhao2001/mygo/internal/log"
+	"github.com/dhao2001/mygo/internal/logging"
 )
 
 // RequestID returns a Gin middleware that ensures every request has a
@@ -19,7 +19,7 @@ func RequestID() gin.HandlerFunc {
 		}
 
 		// Inject into Go context for slog.*Context calls.
-		c.Request = c.Request.WithContext(mygolog.WithRequestID(c.Request.Context(), reqID))
+		c.Request = c.Request.WithContext(logging.WithRequestID(c.Request.Context(), reqID))
 
 		// Also set in Gin context for direct access.
 		c.Set("req_id", reqID)