Add reload and restart buttons to Server tab

Adds ability to reload or restart fail2ban service from the Server tab UI.

Backend changes:
- Add new restart() method to jail_service.py that sends 'restart' command
- Add new POST /api/config/restart endpoint in config router
- Endpoint returns 204 on success, 502 if fail2ban unreachable
- Includes structured logging via 'fail2ban_restarted' log entry

Frontend changes:
- Add configRestart endpoint to endpoints.ts
- Add restartFail2Ban() API function in config.ts API module
- Import ArrowSync24Regular icon from Fluent UI
- Add reload and restart button handlers to ServerTab
- Display 'Reload fail2ban' and 'Restart fail2ban' buttons in action row
- Show loading spinner during operation
- Display success/error MessageBar with appropriate feedback
- Update ServerTab docstring to document new buttons

All 115 frontend tests pass.

backend/app/routers/config.py

@@ -366,6 +366,40 @@ async def reload_fail2ban(
         raise _bad_gateway(exc) from exc
 
 
+# Restart endpoint
+# ---------------------------------------------------------------------------
+
+
+@router.post(
+    "/restart",
+    status_code=status.HTTP_204_NO_CONTENT,
+    summary="Restart the fail2ban service",
+)
+async def restart_fail2ban(
+    request: Request,
+    _auth: AuthDep,
+) -> None:
+    """Trigger a full fail2ban service restart.
+
+    The fail2ban daemon is completely stopped and then started again,
+    re-reading all configuration files in the process.
+
+    Args:
+        request: Incoming request.
+        _auth: Validated session.
+
+    Raises:
+        HTTPException: 502 when fail2ban is unreachable.
+    """
+    socket_path: str = request.app.state.settings.fail2ban_socket
+    try:
+        # Perform restart by sending the restart command via the fail2ban socket.
+        # If fail2ban is not running, this will raise an exception, and we return 502.
+        await jail_service.restart(socket_path)
+    except Fail2BanConnectionError as exc:
+        raise _bad_gateway(exc) from exc
+
+
 # ---------------------------------------------------------------------------
 # Regex tester (stateless)
 # ---------------------------------------------------------------------------

backend/app/services/jail_service.py

@@ -596,6 +596,29 @@ async def reload_all(
             raise JailOperationError(str(exc)) from exc
 
 
+async def restart(socket_path: str) -> None:
+    """Restart the fail2ban service (daemon).
+
+    Sends the 'restart' command to the fail2ban daemon via the Unix socket.
+    All jails are stopped and the daemon is restarted, re-reading all
+    configuration from scratch.
+
+    Args:
+        socket_path: Path to the fail2ban Unix domain socket.
+
+    Raises:
+        JailOperationError: If fail2ban reports the operation failed.
+        ~app.utils.fail2ban_client.Fail2BanConnectionError: If the socket
+            cannot be reached.
+    """
+    client = Fail2BanClient(socket_path=socket_path, timeout=_SOCKET_TIMEOUT)
+    try:
+        _ok(await client.send(["restart"]))
+        log.info("fail2ban_restarted")
+    except ValueError as exc:
+        raise JailOperationError(str(exc)) from exc
+
+
 # ---------------------------------------------------------------------------
 # Public API — Ban / Unban
 # ---------------------------------------------------------------------------