refactor!: rebrand miti99bot to tiennm99bot

BREAKING CHANGE: the Go module path is now github.com/tiennm99/tiennm99bot,
the default sticker pack is stickers_by_<bot username>, and the health body,
deploy DM, User-Agents and image names say tiennm99bot.

cmd/server/command_menu.go

@@ -8,7 +8,7 @@ import (
 	"github.com/go-telegram/bot"
 	"github.com/go-telegram/bot/models"
 
-	"github.com/tiennm99/miti99bot/internal/modules"
+	"github.com/tiennm99/tiennm99bot/internal/modules"
 )
 
 const commandMenuTimeout = 8 * time.Second