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/handler/handler.go

@@ -8,8 +8,8 @@ import (
 	"github.com/gin-gonic/gin"
 	"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"
 )
 
 // Register attaches every API route to the engine.
@@ -46,7 +46,7 @@ func healthCheck(c *gin.Context) {
 }
 
 func versionInfo(c *gin.Context) {
-	c.JSON(200, gin.H{"name": "MMTL", "version": "0.1.0"})
+	c.JSON(200, gin.H{"name": "MeBox", "version": "0.1.0"})
 }
 
 // ─── 权限 Handler 包装 ────────────────────────────────────────────────────────