Rebrand MMTL to MeBox (name, logo, Docker image) (#17)

* Rebrand MMTL to MeBox across codebase and assets

Rename the project display name, Go module path, environment variable
prefix (MEBOX_*), Docker image references, and UI branding from MMTL/mmtl
to MeBox/mebox. Replace logo assets with the new MeBox icon and keep
legacy SQLite migration support for existing mmtl.db deployments.

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* Fix logo icons: use cube-only crop without truncated text

Previous icon generation cropped too much of the source image, including
partial MeBox wordmark text that was cut off in square icon containers.
Regenerate logo-64/192/512, favicon, and SVG from cube-only region.

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

internal/service/backup.go

@@ -19,7 +19,7 @@ import (
 	"go.uber.org/zap"
 	"gorm.io/gorm"
 
-	"github.com/ShukeBta/MMTL/internal/config"
+	"github.com/truewhile/MeBox/internal/config"
 )
 
 // BackupService manages database backups.
@@ -72,7 +72,7 @@ func (b *BackupService) Create(ctx context.Context) (*BackupInfo, error) {
 		return nil, err
 	}
 	ts := time.Now().Format("20060102_150405")
-	dst := filepath.Join(dir, fmt.Sprintf("mmtl_%s.db", ts))
+	dst := filepath.Join(dir, fmt.Sprintf("mebox_%s.db", ts))
 
 	// VACUUM INTO creates a clean, non-WAL copy atomically.
 	if err := b.db.WithContext(ctx).Exec("VACUUM INTO ?", dst).Error; err != nil {