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/api/endpoints.ts

@@ -58,9 +58,12 @@ export const ENDPOINTS = {
   // -------------------------------------------------------------------------
   configJails: "/config/jails",
   configJail: (name: string): string => `/config/jails/${encodeURIComponent(name)}`,
+  configJailLogPath: (name: string): string =>
+    `/config/jails/${encodeURIComponent(name)}/logpath`,
   configGlobal: "/config/global",
   configReload: "/config/reload",
   configRegexTest: "/config/regex-test",
+  configPreviewLog: "/config/preview-log",
 
   // -------------------------------------------------------------------------
   // Server settings