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.

internal/server/health.go

@@ -17,6 +17,6 @@ func HealthHandler() http.HandlerFunc {
 			return
 		}
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-		_, _ = w.Write([]byte("miti99bot ok\n"))
+		_, _ = w.Write([]byte("tiennm99bot ok\n"))
 	}
 }

internal/server/log_middleware.go

@@ -5,7 +5,7 @@ import (
 	"runtime/debug"
 	"time"
 
-	"github.com/tiennm99/miti99bot/internal/log"
+	"github.com/tiennm99/tiennm99bot/internal/log"
 )
 
 // statusRecorder wraps http.ResponseWriter to capture the final status

internal/server/log_middleware_test.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 	"testing"
 
-	logger "github.com/tiennm99/miti99bot/internal/log"
+	logger "github.com/tiennm99/tiennm99bot/internal/log"
 )
 
 // captureLogger swaps the package-level logger for one writing to buf and