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/pages/BlocklistsPage.tsx

@@ -8,7 +8,7 @@ const useStyles = makeStyles({
   root: { padding: tokens.spacingVerticalXXL },
 });
 
-export function BlocklistsPage(): JSX.Element {
+export function BlocklistsPage(): React.JSX.Element {
   const styles = useStyles();
   return (
     <div className={styles.root}>

frontend/src/pages/HistoryPage.tsx

@@ -8,7 +8,7 @@ const useStyles = makeStyles({
   root: { padding: tokens.spacingVerticalXXL },
 });
 
-export function HistoryPage(): JSX.Element {
+export function HistoryPage(): React.JSX.Element {
   const styles = useStyles();
   return (
     <div className={styles.root}>

frontend/src/pages/LoginPage.tsx

@@ -71,7 +71,7 @@ const useStyles = makeStyles({
 /**
  * Login page — single password input, no username.
  */
-export function LoginPage(): JSX.Element {
+export function LoginPage(): React.JSX.Element {
   const styles = useStyles();
   const navigate = useNavigate();
   const [searchParams] = useSearchParams();

frontend/src/pages/MapPage.tsx

@@ -8,7 +8,7 @@ const useStyles = makeStyles({
   root: { padding: tokens.spacingVerticalXXL },
 });
 
-export function MapPage(): JSX.Element {
+export function MapPage(): React.JSX.Element {
   const styles = useStyles();
   return (
     <div className={styles.root}>

frontend/src/pages/SetupPage.tsx

@@ -96,7 +96,7 @@ const DEFAULT_VALUES: FormValues = {
  * First-run setup wizard page.
  * Collects master password and server preferences.
  */
-export function SetupPage(): JSX.Element {
+export function SetupPage(): React.JSX.Element {
   const styles = useStyles();
   const navigate = useNavigate();