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/types/config.ts

@@ -0,0 +1,130 @@
+/**
+ * TypeScript interfaces for the configuration and server settings API.
+ */
+
+// ---------------------------------------------------------------------------
+// Jail Configuration
+// ---------------------------------------------------------------------------
+
+export interface JailConfig {
+  name: string;
+  ban_time: number;
+  max_retry: number;
+  find_time: number;
+  fail_regex: string[];
+  ignore_regex: string[];
+  log_paths: string[];
+  date_pattern: string | null;
+  log_encoding: string;
+  backend: string;
+  actions: string[];
+}
+
+export interface JailConfigResponse {
+  jail: JailConfig;
+}
+
+export interface JailConfigListResponse {
+  jails: JailConfig[];
+  total: number;
+}
+
+export interface JailConfigUpdate {
+  ban_time?: number | null;
+  max_retry?: number | null;
+  find_time?: number | null;
+  fail_regex?: string[] | null;
+  ignore_regex?: string[] | null;
+  date_pattern?: string | null;
+  dns_mode?: string | null;
+  enabled?: boolean | null;
+}
+
+// ---------------------------------------------------------------------------
+// Global Configuration
+// ---------------------------------------------------------------------------
+
+export interface GlobalConfig {
+  log_level: string;
+  log_target: string;
+  db_purge_age: number;
+  db_max_matches: number;
+}
+
+export interface GlobalConfigUpdate {
+  log_level?: string | null;
+  log_target?: string | null;
+  db_purge_age?: number | null;
+  db_max_matches?: number | null;
+}
+
+// ---------------------------------------------------------------------------
+// Server Settings
+// ---------------------------------------------------------------------------
+
+export interface ServerSettings {
+  log_level: string;
+  log_target: string;
+  syslog_socket: string | null;
+  db_path: string;
+  db_purge_age: number;
+  db_max_matches: number;
+}
+
+export interface ServerSettingsResponse {
+  settings: ServerSettings;
+}
+
+export interface ServerSettingsUpdate {
+  log_level?: string | null;
+  log_target?: string | null;
+  db_purge_age?: number | null;
+  db_max_matches?: number | null;
+}
+
+// ---------------------------------------------------------------------------
+// Regex Tester
+// ---------------------------------------------------------------------------
+
+export interface RegexTestRequest {
+  log_line: string;
+  fail_regex: string;
+}
+
+export interface RegexTestResponse {
+  matched: boolean;
+  groups: string[];
+  error: string | null;
+}
+
+// ---------------------------------------------------------------------------
+// Log Preview
+// ---------------------------------------------------------------------------
+
+export interface LogPreviewRequest {
+  log_path: string;
+  fail_regex: string;
+  num_lines?: number;
+}
+
+export interface LogPreviewLine {
+  line: string;
+  matched: boolean;
+  groups: string[];
+}
+
+export interface LogPreviewResponse {
+  lines: LogPreviewLine[];
+  total_lines: number;
+  matched_count: number;
+  regex_error: string | null;
+}
+
+// ---------------------------------------------------------------------------
+// Add Log Path
+// ---------------------------------------------------------------------------
+
+export interface AddLogPathRequest {
+  log_path: string;
+  tail?: boolean;
+}