Merge Log tab into Server tab and remove Log tab

The Log tab provided a service health panel and log viewer. These are
consolidated into the Server tab with a new ServerHealthSection component
that encapsulates all log-related functionality.

- Extract service health panel and log viewer into ServerHealthSection component
- Add severity-based log line color coding (ERROR=red, WARNING=yellow, DEBUG=gray)
- Implement log filtering, line count selection, and auto-refresh controls
- Scroll to bottom when new log data arrives
- Render health metrics grid with version, jail count, bans, failures
- Show read-only log level and log target in health section
- Handle non-file targets with informational banner
- Import ServerHealthSection in ServerTab and render after map thresholds
- Remove LogTab component import from ConfigPage
- Remove 'log' from TabValue type
- Remove Log tab element from TabList
- Remove conditional render for LogTab
- Remove LogTab from barrel export (index.ts)
- Delete LogTab.tsx and LogTab.test.tsx files
- Update ConfigPage docstring

All 115 frontend tests pass (8 fewer due to deleted LogTab tests).

frontend/src/components/config/ServerTab.tsx

@@ -2,8 +2,8 @@
  * ServerTab — fail2ban server-level settings editor.
  *
  * Provides form fields for live server settings (log level, log target,
- * DB purge age, DB max matches), a "Flush Logs" action button, and
- * world map color threshold configuration.
+ * DB purge age, DB max matches), a "Flush Logs" action button,
+ * world map color threshold configuration, and service health + log viewer.
  */
 
 import { useCallback, useEffect, useMemo, useState } from "react";
@@ -31,6 +31,7 @@ import {
   updateMapColorThresholds,
 } from "../../api/config";
 import { AutoSaveIndicator } from "./AutoSaveIndicator";
+import { ServerHealthSection } from "./ServerHealthSection";
 import { useConfigStyles } from "./configStyles";
 
 /** Available fail2ban log levels in descending severity order. */
@@ -354,6 +355,9 @@ export function ServerTab(): React.JSX.Element {
           </Text>
         </div>
       ) : null}
+
+      {/* Service Health & Log Viewer section */}
+      <ServerHealthSection />
     </div>
   );
 }