Integrate symbols/ into main repo

- Added symbols/ folder (previously separate repo)
- Removed symbols/ from .gitignore
- Updated CLAUDE.md documentation
- Deleted separate Symbols repo on Gitea

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -13,7 +13,6 @@ node_modules/
 # Temp files
 *.tmp
 *.bak
-symbols/
 kostenschaetzung/
 schadendokumentation/
 zeitwert/