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/fanart.go

@@ -21,7 +21,7 @@ import (
 
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
+	"github.com/truewhile/MeBox/internal/config"
 )
 
 // FanartProvider talks to https://webservice.fanart.tv.
@@ -133,7 +133,7 @@ func (f *FanartProvider) getJSON(ctx context.Context, u string, out any) error {
 	if err != nil {
 		return err
 	}
-	req.Header.Set("User-Agent", "MMTL/0.1")
+	req.Header.Set("User-Agent", "MeBox/0.1")
 	resp, err := f.client.Do(req)
 	if err != nil {
 		return err