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/danmaku_match_test.go

@@ -16,8 +16,8 @@ import (
 
 	"github.com/stretchr/testify/require"
 
-	"github.com/ShukeBta/MMTL/internal/model"
-	"github.com/ShukeBta/MMTL/internal/service/cloud"
+	"github.com/truewhile/MeBox/internal/model"
+	"github.com/truewhile/MeBox/internal/service/cloud"
 )
 
 // overrideDanmakuOfficialBase points the "official" endpoint (match + fallback)
@@ -34,7 +34,7 @@ func overrideDanmakuOfficialBase(t *testing.T, base string) {
 // since the file is smaller than the 16MB prefix).
 func writeDanmakuTestVideo(t *testing.T, name string) (path, wantHash string) {
 	t.Helper()
-	content := bytes.Repeat([]byte("MMTL-danmaku-hash-test-0123456789"), 500)
+	content := bytes.Repeat([]byte("MeBox-danmaku-hash-test-0123456789"), 500)
 	path = filepath.Join(t.TempDir(), name)
 	require.NoError(t, os.WriteFile(path, content, 0o644))
 	sum := md5.Sum(content)