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/service.go

@@ -1,4 +1,4 @@
-// Package service 包含 MMTL 的业务逻辑。
+// Package service 包含 MeBox 的业务逻辑。
 // Handler 反序列化 HTTP 请求，调用 Service 方法，然后序列化响应。
 // Services 拥有所有横切策略（认证、扫描、转码等）且不直接处理 HTTP 类型。
 package service
@@ -9,8 +9,8 @@ import (
 
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
-	"github.com/ShukeBta/MMTL/internal/repository"
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/repository"
 )
 
 // Container 持有在启动时初始化的每个服务。Handler 接收指向它的指针并选择相关字段。