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/image_proxy.go

@@ -2,7 +2,7 @@
 //
 // Some deployments cannot reach image.tmdb.org directly (GFW, internal-only
 // networks). ImageProxy fronts a remote image URL so the browser only ever
-// talks to the MMTL origin. The proxy:
+// talks to the MeBox origin. The proxy:
 //
 //   - validates the URL scheme is http/https,
 //   - streams bytes through with a small disk cache under cache/images,
@@ -20,7 +20,7 @@ import (
 
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
+	"github.com/truewhile/MeBox/internal/config"
 )
 
 // ImageProxy fetches and caches remote images on behalf of the browser.