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/cloud/pan115_openapi.go

@@ -22,7 +22,7 @@ import (
 	"path/filepath"
 	"strings"
 
-	"github.com/ShukeBta/MMTL/internal/service/cloud115"
+	"github.com/truewhile/MeBox/internal/service/cloud115"
 )
 
 // OpenAPI115Provider 暴露 115 开放平台驱动接口。
@@ -112,7 +112,7 @@ func (p *openAPI115Provider) OpenClient() *cloud115.OpenClient { return p.c }
 // io.Reader 无法携带文件名，因此走独立的 named 上传接口。将内容落为临时文件后
 // 重命名为目标文件名，再交给 115 上传（/open/upload/init 的 file_name 取真实文件名）。
 func (p *openAPI115Provider) PutFileNamed(ctx context.Context, parentCID, fileName string, r io.Reader) error {
-	tmp, err := os.CreateTemp("", "mmtl-upload-*")
+	tmp, err := os.CreateTemp("", "mebox-upload-*")
 	if err != nil {
 		return fmt.Errorf("115: 创建临时文件失败：%w", err)
 	}