chore: sloppyslop working state — bump submodules + env/ignore/CLAUDE docs

Point mcma-backend + mcma-webui at their sloppyslop tips (lyrics, transcoding,
admin/storage/maintenance/instance UI, batch metadata, NowPlaying+lyrics).
Includes the CORS note in .env.example, TODO/ ignore, and the project CLAUDE.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,7 @@
 .env
 *.zip
 plans/
+TODO/
 modern-sk/
 data/
 .DS_Store