Clean up repository: remove temporary files and outdated documentation

- Remove temporary files: .env.bak, temp-elo-data/ (46MB)
- Remove outdated documentation: cleanup_plan.md, IMPLEMENTATION_SUMMARY.md, QUICK_COMMANDS.md, SETUP_GUIDE.md, TEST_RESULTS.md
- Remove outdated config.example (replaced by env.example)
- Remove empty directories: backend/src/main/resources/static, templates
- Enhance .gitignore to cover more temporary file patterns (*.bak, *.old, *.tmp, *.swp, *.swo, *~)

Total: Removed 541 lines of outdated/temporary content

Author: Alexander-Rees

.gitignore

@@ -74,4 +74,10 @@ backend/.mvn/
 
 # Temporary files
 .env.bak
+*.bak
+*.old
+*.tmp
 temp-elo-data/
+*.swp
+*.swo
+*~