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/runtime_cache.go

@@ -10,7 +10,7 @@ import (
 	"github.com/redis/go-redis/v9"
 	"go.uber.org/zap"
 
-	"github.com/ShukeBta/MMTL/internal/config"
+	"github.com/truewhile/MeBox/internal/config"
 )
 
 type RuntimeCacheService struct {
@@ -35,7 +35,7 @@ func NewRuntimeCacheService(cfg *config.Config, log *zap.Logger) *RuntimeCacheSe
 	}
 	c.prefix = strings.Trim(strings.TrimSpace(cfg.Cache.RedisPrefix), ":")
 	if c.prefix == "" {
-		c.prefix = "mmtl"
+		c.prefix = "mebox"
 	}
 	rawURL := strings.TrimSpace(cfg.Cache.RedisURL)
 	if rawURL == "" {