Move backend files to root level for cleaner GitHub display

- Move all backend files from swingmusic/ to root level
- Backend files now display directly on GitHub repository page
- Keep client applications as submodules (swingmusic-android, swingmusic-desktop, swingmusic-webclient)
- Update README to reflect new structure (no cd swingmusic needed)
- Cleaner, more professional GitHub repository layout

Files moved to root:
- src/ (main source code)
- pyproject.toml, requirements.txt, run.py
- swingmusic.spec, uv.lock, version.txt
- services/

Result: GitHub shows backend files directly while maintaining organized structure

README.md

@@ -59,9 +59,6 @@ This repository includes client applications as submodules:
 git clone --recurse-submodules https://github.com/Dvorinka/swingmusic-extended.git
 cd swingmusic-extended
 
-# Navigate to backend
-cd swingmusic
-
 # Install dependencies
 uv sync