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/router.go

@@ -11,12 +11,12 @@ import (
 	"github.com/gin-gonic/gin"
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
-	"github.com/ShukeBta/MMTL/internal/handler"
-	"github.com/ShukeBta/MMTL/internal/middleware"
-	"github.com/ShukeBta/MMTL/internal/service"
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/handler"
+	"github.com/truewhile/MeBox/internal/middleware"
+	"github.com/truewhile/MeBox/internal/service"
 
-	"github.com/ShukeBta/MMTL/web"
+	"github.com/truewhile/MeBox/web"
 )
 
 func buildRouter(cfg *config.Config, logger *zap.Logger, svc *service.Container) *gin.Engine {
@@ -78,7 +78,7 @@ func serveSPA(r *gin.Engine, root fs.FS) {
 		setNoCacheHeaders(c)
 		data, err := fs.ReadFile(root, "index.html")
 		if err != nil {
-			c.String(http.StatusNotFound, "MMTL web UI not found")
+			c.String(http.StatusNotFound, "MeBox web UI not found")
 			return
 		}
 		c.Data(http.StatusOK, "text/html; charset=utf-8", data)