feat: merge chess_tutor + OpenRouter abstraction

- Merged stefan-kp/chess_tutor into chess-project with full feature set
- Preserved Hermes agent files (agents/, .gitea/, AGENTS.md)
- Added OpenRouter abstraction layer (src/lib/openrouter.ts)
- Created ModelSelector dropdown component with 9 models
- Updated API routes (chat + opening explanation) to use OpenRouter
- Updated useTutorChat to route through OpenRouter API
- Updated onboarding and API key input for OpenRouter
- Created tasks.md with sprint 1 plan
- Updated README with new architecture details

.gitea/pull_request_template.md

@@ -0,0 +1,23 @@
+## Summary
+
+## Type of Change
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactoring
+- [ ] Documentation
+- [ ] Other: 
+
+## Related Task / Issue
+
+Reference the task from `/tasks` or a planning issue from `core-planning`.
+
+## Testing
+
+- [ ] Unit tests added/updated
+- [ ] Manual testing completed
+- [ ] All existing tests pass
+
+## Checklist
+- [ ] Code follows project style guidelines
+- [ ] Self-review completed
+- [ ] Documentation updated (if needed)