Expose usedns, date_pattern, and prefregex in jail config UI

- Add use_dns and prefregex fields to JailConfig model (backend + frontend types)
- Add prefregex to JailConfigUpdate; validate as regex before writing
- Fetch usedns and prefregex in get_jail_config via asyncio.gather
- Write usedns and prefregex in update_jail_config
- ConfigPage JailAccordionPanel: editable date_pattern input, dns_mode
  Select dropdown (yes/warn/no/raw), and prefregex input
- 8 new service unit tests + 3 new router integration tests
- 628 tests pass; 85% line coverage; ruff/mypy/tsc/eslint clean

frontend/src/components/__tests__/ConfigPageLogPath.test.tsx

@@ -116,6 +116,8 @@ const MOCK_JAIL: JailConfig = {
   date_pattern: null,
   log_encoding: "UTF-8",
   backend: "auto",
+  use_dns: "warn",
+  prefregex: "",
   actions: [],
   bantime_escalation: null,
 };

frontend/src/pages/ConfigPage.tsx

@@ -254,6 +254,9 @@ function JailAccordionPanel({
   const [failRegex, setFailRegex] = useState<string[]>(jail.fail_regex);
   const [ignoreRegex, setIgnoreRegex] = useState<string[]>(jail.ignore_regex);
   const [logPaths, setLogPaths] = useState<string[]>(jail.log_paths);
+  const [datePattern, setDatePattern] = useState(jail.date_pattern ?? "");
+  const [dnsMode, setDnsMode] = useState(jail.use_dns);
+  const [prefRegex, setPrefRegex] = useState(jail.prefregex);
   const [deletingPath, setDeletingPath] = useState<string | null>(null);
   const [newLogPath, setNewLogPath] = useState("");
   const [newLogPathTail, setNewLogPathTail] = useState(true);
@@ -331,6 +334,9 @@ function JailAccordionPanel({
         max_retry: Number(maxRetry) || jail.max_retry,
         fail_regex: failRegex,
         ignore_regex: ignoreRegex,
+        date_pattern: datePattern !== "" ? datePattern : null,
+        dns_mode: dnsMode,
+        prefregex: prefRegex !== "" ? prefRegex : null,
         bantime_escalation: escalation,
       });
       setMsg({ text: "Saved.", ok: true });
@@ -346,6 +352,9 @@ function JailAccordionPanel({
     maxRetry,
     failRegex,
     ignoreRegex,
+    datePattern,
+    dnsMode,
+    prefRegex,
     escEnabled,
     escFactor,
     escFormula,
@@ -404,6 +413,41 @@ function JailAccordionPanel({
           <Input readOnly value={jail.log_encoding} />
         </Field>
       </div>
+      <div className={styles.fieldRow}>
+        <Field label="Date Pattern" hint="Leave blank for auto-detect.">
+          <Input
+            className={styles.codeFont}
+            placeholder="auto-detect"
+            value={datePattern}
+            onChange={(_e, d) => {
+              setDatePattern(d.value);
+            }}
+          />
+        </Field>
+        <Field label="DNS Mode">
+          <Select
+            value={dnsMode}
+            onChange={(_e, d) => {
+              setDnsMode(d.value);
+            }}
+          >
+            <option value="yes">yes — resolve hostnames</option>
+            <option value="warn">warn — resolve and warn</option>
+            <option value="no">no — skip hostname resolution</option>
+            <option value="raw">raw — use value as-is</option>
+          </Select>
+        </Field>
+      </div>
+      <Field label="Prefix Regex" hint="Prepended to every failregex for pre-filtering. Leave blank to disable.">
+        <Input
+          className={styles.codeFont}
+          placeholder="e.g. ^%(__prefix_line)s"
+          value={prefRegex}
+          onChange={(_e, d) => {
+            setPrefRegex(d.value);
+          }}
+        />
+      </Field>
       <Field label="Log Paths">
         {logPaths.length === 0 ? (
           <Text className={styles.infoText} size={200}>

frontend/src/types/config.ts

@@ -50,6 +50,10 @@ export interface JailConfig {
   date_pattern: string | null;
   log_encoding: string;
   backend: string;
+  /** DNS look-up mode reported by fail2ban: "yes" | "warn" | "no" | "raw". */
+  use_dns: string;
+  /** Prefix regex prepended to every failregex; empty string means disabled. */
+  prefregex: string;
   actions: string[];
   bantime_escalation: BantimeEscalation | null;
 }
@@ -69,6 +73,8 @@ export interface JailConfigUpdate {
   find_time?: number | null;
   fail_regex?: string[] | null;
   ignore_regex?: string[] | null;
+  /** Prefix regex; undefined/null = skip, "" = clear, non-empty = set. */
+  prefregex?: string | null;
   date_pattern?: string | null;
   dns_mode?: string | null;
   enabled?: boolean | null;