Stage 7: configuration view — backend service, routers, tests, and frontend

- config_service.py: read/write jail config via asyncio.gather, global
  settings, in-process regex validation, log preview via _read_tail_lines
- server_service.py: read/write server settings, flush logs
- config router: 9 endpoints for jail/global config, regex-test,
  logpath management, log preview
- server router: GET/PUT settings, POST flush-logs
- models/config.py expanded with JailConfig, GlobalConfigUpdate,
  LogPreview* models
- 285 tests pass (68 new), ruff clean, mypy clean (44 files)
- Frontend: types/config.ts, api/config.ts, hooks/useConfig.ts,
  ConfigPage.tsx full implementation (Jails accordion editor,
  Global config, Server settings, Regex Tester with preview)
- Fixed pre-existing frontend lint: JSX.Element → React.JSX.Element
  (10 files), void/promise patterns in useServerStatus + useJails,
  no-misused-spread in client.ts, eslint.config.ts self-excluded

frontend/src/components/RequireAuth.tsx

@@ -11,7 +11,7 @@ import { useAuth } from "../providers/AuthProvider";
 
 interface RequireAuthProps {
   /** The protected page content to render when authenticated. */
-  children: JSX.Element;
+  children: React.JSX.Element;
 }
 
 /**
@@ -20,7 +20,7 @@ interface RequireAuthProps {
  * Redirects to `/login?next=<path>` otherwise so the intended destination is
  * preserved and honoured after a successful login.
  */
-export function RequireAuth({ children }: RequireAuthProps): JSX.Element {
+export function RequireAuth({ children }: RequireAuthProps): React.JSX.Element {
   const { isAuthenticated } = useAuth();
   const location = useLocation();
 

frontend/src/components/ServerStatusBar.tsx

@@ -81,7 +81,7 @@ const useStyles = makeStyles({
  * Render this at the top of the dashboard page (and any page that should
  * show live server status).
  */
-export function ServerStatusBar(): JSX.Element {
+export function ServerStatusBar(): React.JSX.Element {
   const styles = useStyles();
   const { status, loading, error, refresh } = useServerStatus();