Add fail2ban log viewer and service health to Config page

Task 2: adds a new Log tab to the Configuration page.

Backend:
- New Pydantic models: Fail2BanLogResponse, ServiceStatusResponse
  (backend/app/models/config.py)
- New service methods in config_service.py:
    read_fail2ban_log() — queries socket for log target/level, validates the
    resolved path against a safe-prefix allowlist (/var/log) to prevent
    path traversal, then reads the tail of the file via the existing
    _read_tail_lines() helper; optional substring filter applied server-side.
    get_service_status() — delegates to health_service.probe() and appends
    log level/target from the socket.
- New endpoints in routers/config.py:
    GET /api/config/fail2ban-log?lines=200&filter=...
    GET /api/config/service-status
  Both require authentication; log endpoint returns 400 for non-file log
  targets or path-traversal attempts, 502 when fail2ban is unreachable.

Frontend:
- New LogTab.tsx component:
    Service Health panel (Running/Offline badge, version, jail count, bans,
    failures, log level/target, offline warning banner).
    Log viewer with color-coded lines (error=red, warning=yellow,
    debug=grey), toolbar (filter input + debounce, lines selector, manual
    refresh, auto-refresh with interval selector), truncation notice, and
    auto-scroll to bottom on data updates.
  fetchData uses Promise.allSettled so a log-read failure never hides the
  service-health panel.
- Types: Fail2BanLogResponse, ServiceStatusResponse (types/config.ts)
- API functions: fetchFail2BanLog, fetchServiceStatus (api/config.ts)
- Endpoint constants (api/endpoints.ts)
- ConfigPage.tsx: Log tab added after existing tabs

Tests:
- Backend service tests: TestReadFail2BanLog (6), TestGetServiceStatus (2)
- Backend router tests: TestGetFail2BanLog (8), TestGetServiceStatus (3)
- Frontend: LogTab.test.tsx (8 tests)

Docs:
- Features.md: Log section added under Configuration View
- Architekture.md: config.py router and config_service.py descriptions updated
- Tasks.md: Task 2 marked done

frontend/src/pages/ConfigPage.tsx

@@ -22,6 +22,7 @@ import {
   FiltersTab,
   GlobalTab,
   JailsTab,
+  LogTab,
   MapTab,
   RegexTesterTab,
   ServerTab,
@@ -60,7 +61,8 @@ type TabValue =
   | "global"
   | "server"
   | "map"
-  | "regex";
+  | "regex"
+  | "log";
 
 export function ConfigPage(): React.JSX.Element {
   const styles = useStyles();
@@ -91,6 +93,7 @@ export function ConfigPage(): React.JSX.Element {
         <Tab value="server">Server</Tab>
         <Tab value="map">Map</Tab>
         <Tab value="regex">Regex Tester</Tab>
+        <Tab value="log">Log</Tab>
       </TabList>
 
       <div className={styles.tabContent} key={tab}>
@@ -101,6 +104,7 @@ export function ConfigPage(): React.JSX.Element {
         {tab === "server" && <ServerTab />}
         {tab === "map" && <MapTab />}
         {tab === "regex" && <RegexTesterTab />}
+        {tab === "log" && <LogTab />}
       </div>
     </div>
   );