feat: Implement domain logic separation with clean architecture

- Created complete domain layer with pure business logic
- Implemented Issue domain models with 48 passing tests
- Implemented Project domain models with 31 passing tests
- Added domain services for complex business operations
- Established clean separation between domain, application, and infrastructure
- All 250 tests passing with no breaking changes

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

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

domain/issues/repositories.py

@@ -0,0 +1,116 @@
+"""
+Repository interfaces for issue domain.
+
+Defines contracts for data access without infrastructure dependencies.
+"""
+
+from abc import ABC, abstractmethod
+from typing import List, Optional, Dict, Any
+from .models import Issue
+
+
+class IssueRepository(ABC):
+    """Repository interface for issue persistence."""
+
+    @abstractmethod
+    async def get_issue(self, issue_number: int) -> Issue:
+        """Retrieve issue by number.
+
+        Args:
+            issue_number: The issue number to retrieve
+
+        Returns:
+            Issue domain object
+
+        Raises:
+            IssueNotFoundError: If issue doesn't exist
+        """
+        pass
+
+    @abstractmethod
+    async def list_issues(self, state: Optional[str] = None, limit: Optional[int] = None) -> List[Issue]:
+        """List issues, optionally filtered by state.
+
+        Args:
+            state: Optional state filter (open, closed)
+            limit: Optional limit on number of results
+
+        Returns:
+            List of Issue domain objects
+        """
+        pass
+
+    @abstractmethod
+    async def save_issue(self, issue: Issue) -> None:
+        """Save issue changes.
+
+        Args:
+            issue: Issue domain object to save
+        """
+        pass
+
+    @abstractmethod
+    async def create_issue(self, title: str, description: str, labels: List[str]) -> Issue:
+        """Create a new issue.
+
+        Args:
+            title: Issue title
+            description: Issue description
+            labels: List of label names
+
+        Returns:
+            Created Issue domain object
+        """
+        pass
+
+    @abstractmethod
+    async def delete_issue(self, issue_number: int) -> None:
+        """Delete an issue.
+
+        Args:
+            issue_number: The issue number to delete
+        """
+        pass
+
+
+class ProjectRepository(ABC):
+    """Repository interface for project information."""
+
+    @abstractmethod
+    async def get_issue_project_info(self, issue_number: int) -> Dict[str, Any]:
+        """Get project information for an issue.
+
+        Args:
+            issue_number: The issue number
+
+        Returns:
+            Dictionary containing project context information
+        """
+        pass
+
+    @abstractmethod
+    async def get_kanban_columns(self) -> List[str]:
+        """Get available kanban columns for the project.
+
+        Returns:
+            List of kanban column names
+        """
+        pass
+
+    @abstractmethod
+    async def get_project_labels(self) -> List[Dict[str, Any]]:
+        """Get available labels for the project.
+
+        Returns:
+            List of label definitions
+        """
+        pass
+
+    @abstractmethod
+    async def get_milestones(self) -> List[Dict[str, Any]]:
+        """Get available milestones for the project.
+
+        Returns:
+            List of milestone information
+        """
+        pass