refactor: extract focused clients from GiteaClient (Slices 1-6)

- Create gitea/issues_client.py with IssuesClient class (9 methods)
- Create gitea/prs_client.py with PullRequestsClient class (17 methods)
- Create gitea/files_client.py with FilesClient class (4 methods)
- Create gitea/notifications_client.py with NotificationsClient class (2 methods)
- Create gitea/repos_client.py with ReposClient class (2 methods)
- Create gitea/__init__.py to export all client classes
- Remove delegation methods from GiteaClient (now ~70 lines)
- Update all callers to use sub-clients (client.issues, client.prs, etc.)
- Update test files to mock sub-client attributes

GiteaClient is now a facade that provides access to focused sub-clients:
- repos: Repository operations (ReposClient)
- issues: Issue operations (IssuesClient)
- prs: Pull request operations (PullRequestsClient)
- files: File and git ref operations (FilesClient)
- notifications: Notification operations (NotificationsClient)

Refs: #godclass-refactor

gitea/repos_client.py

@@ -0,0 +1,72 @@
+"""Repositories client for Gitea API operations."""
+
+import logging
+from typing import Any
+
+import httpx
+
+from .models import RepositoryModel, UserModel
+
+
+logger: logging.Logger = logging.getLogger("gitea.repos_client")
+
+
+class ReposClient:
+    """HTTP client for Gitea Repositories API operations."""
+
+    def __init__(self, base_url: str, client: httpx.Client, org_filter: str) -> None:
+        """Initialize the ReposClient.
+
+        Args:
+            base_url: The base URL for the Gitea API.
+            client: The httpx client for making requests.
+            org_filter: Organization filter for repositories.
+        """
+        self.base_url: str = base_url
+        self.client: httpx.Client = client
+        self.org_filter: str = org_filter
+
+    def list_all_user_repos(self) -> list[RepositoryModel]:
+        """List all repositories for the authenticated user.
+
+        Returns:
+            List of repositories belonging to the configured organization.
+        """
+        try:
+            url = f"{self.base_url}/api/v1/user/repos"
+            response = self.client.get(url)
+            response.raise_for_status()
+            repos: list[dict[str, Any]] = response.json()
+            # Filter to ONLY configured organization repos, include mirrors
+            seen: set[str] = set()
+            result: list[RepositoryModel] = []
+            for r in repos:
+                full_name = r.get("full_name", "")
+                if (
+                    full_name
+                    and full_name not in seen
+                    and (r.get("owner") or {}).get("login") == self.org_filter
+                ):
+                    seen.add(full_name)
+                    result.append(RepositoryModel(**r))
+            return result
+        except Exception as e:
+            logger.error(f"Error listing user repos: {e}", exc_info=True)
+            return []
+
+    def get_authenticated_user(self) -> UserModel:
+        """Get the authenticated user.
+
+        Returns:
+            The authenticated user.
+
+        Raises:
+            RuntimeError: If the user cannot be retrieved.
+        """
+        try:
+            response = self.client.get(f"{self.base_url}/api/v1/user")
+            response.raise_for_status()
+            return UserModel(**response.json())
+        except Exception as e:
+            logger.error(f"Error getting authenticated user: {e}", exc_info=True)
+            raise RuntimeError(f"Could not get authenticated user: {e}") from e