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>

cmd/server/server_manager.go

@@ -13,8 +13,8 @@ import (
 
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
-	"github.com/ShukeBta/MMTL/internal/service"
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/service"
 )
 
 // tlsPair 记录当前正在服务的证书，用于判断是否需要重新绑定监听。
@@ -27,7 +27,7 @@ type tlsPair struct {
 	version string
 }
 
-// serverManager 负责 MMTL 的 HTTP/HTTPS 监听。HTTPS 设置保存后调用 Reload，
+// serverManager 负责 MeBox 的 HTTP/HTTPS 监听。HTTPS 设置保存后调用 Reload，
 // 在同一个端口上把明文 HTTP 与 TLS 监听热切换，无需重启进程：
 //
 //   - 关闭旧监听释放端口（同一进程内 Windows 不允许重复绑定同一端口）；