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/notifications_client.py

@@ -0,0 +1,78 @@
+"""Notifications client for Gitea API operations."""
+
+import logging
+from typing import Any, Optional
+
+import httpx
+
+
+logger: logging.Logger = logging.getLogger("gitea.notifications_client")
+
+
+class NotificationsClient:
+    """HTTP client for Gitea Notifications API operations."""
+
+    def __init__(self, base_url: str, client: httpx.Client, org_filter: str) -> None:
+        """Initialize the NotificationsClient.
+
+        Args:
+            base_url: The base URL for the Gitea API.
+            client: The httpx client for making requests.
+            org_filter: Organization filter for notifications.
+        """
+        self.base_url: str = base_url
+        self.client: httpx.Client = client
+        self.org_filter: str = org_filter
+
+    def list_unread_notifications(
+        self, since: Optional[str] = None
+    ) -> list[dict[str, Any]]:
+        """List unread notifications.
+
+        Args:
+            since: Optional ISO 8601 timestamp to filter notifications after.
+
+        Returns:
+            List of unread notifications for the configured organization.
+        """
+        try:
+            url = f"{self.base_url}/api/v1/notifications"
+            params: dict[str, str] = {"all": "false"}
+            if since:
+                params["since"] = since
+            response = self.client.get(url, params=params)
+            response.raise_for_status()
+            notifications: list[dict[str, Any]] = response.json()
+
+            result: list[dict[str, Any]] = []
+            for n in notifications:
+                repo_info = n.get("repository") or {}
+                owner_info = repo_info.get("owner") or {}
+                owner_login = owner_info.get("login", "")
+                if owner_login == self.org_filter:
+                    result.append(n)
+            return result
+        except Exception as e:
+            logger.error(f"Error listing unread notifications: {e}", exc_info=True)
+            return []
+
+    def mark_notification_as_read(self, thread_id: int) -> bool:
+        """Mark a notification as read.
+
+        Args:
+            thread_id: Notification thread ID.
+
+        Returns:
+            True if successful, False otherwise.
+        """
+        try:
+            url = f"{self.base_url}/api/v1/notifications/threads/{thread_id}"
+            response = self.client.patch(url)
+            response.raise_for_status()
+            return True
+        except Exception as e:
+            logger.error(
+                f"Error marking notification thread {thread_id} as read: {e}",
+                exc_info=True,
+            )
+            return False