feat: Implement comprehensive IssueCreator system and create CLI roadmap issues

IssueCreator Implementation:
- Add tddai/issue_creator.py with full POST API functionality for issue creation
- Support multiple creation methods: basic, enhancement, bug, template-based
- Include structured issue formatting with acceptance criteria and dependencies
- Template system with variable substitution for reusable issue creation

Authentication Fix:
- Fix critical authentication bug: use GITEA_API_TOKEN instead of GITEA_TOKEN
- Update both IssueCreator and IssueWriter for consistency
- Update all tests and documentation to reflect correct environment variable

Comprehensive Test Suite:
- Add 15 unit tests for IssueCreator (tests/test_issue_creator.py)
- Add 5 integration tests for full API lifecycle (tests/test_issue_integration.py)
- Create test_environment_variable_detection to prevent future auth issues
- Total 33 tests covering complete issue handling workflow

CLI Integration:
- Enhance tddai_cli.py with 3 new commands: create-issue, create-enhancement, create-from-template
- Add comprehensive argument parsing with optional fields and priority support
- Include user-friendly output with next step guidance
- Update package exports to include IssueCreator

CLI Roadmap Execution:
- Successfully create 8 CLI implementation issues (#12-#19) in Gitea
- Resolve mismatch between NEXT.md roadmap and actual Gitea issues
- Issues prioritized for core USPs: Database Query CLI and AST Query CLI
- Remove local MISSING_ISSUES.md file after successful creation

Framework Maturity:
- Complete CRUD operations for issue management (Create, Read, Update, Delete)
- Robust error handling and API integration patterns
- Full authentication and environment variable management
- Ready for production CLI implementation workflow

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

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

tests/test_issue_writer.py

@@ -34,7 +34,7 @@ class TestIssueWriter:
     def test_init_without_auth_token_uses_env(self):
         """Test IssueWriter uses environment variable when no token provided."""
         config = self._get_test_config()
-        with patch.dict('os.environ', {'GITEA_TOKEN': 'env-token'}):
+        with patch.dict('os.environ', {'GITEA_API_TOKEN': 'env-token'}):
             writer = IssueWriter(config=config)
             assert writer.auth_token == "env-token"