feat(frontend): add config hooks for jail, action, filter, and auto-save

- useJailFileConfig: manages jail.local section state with dirty tracking
- useActionConfig: manages action .conf file state
- useFilterConfig: manages filter .conf file state
- useAutoSave: debounced auto-save with status indicator support

frontend/src/hooks/useJailFileConfig.ts

@@ -0,0 +1,76 @@
+/**
+ * React hook for loading and updating a single parsed jail.d config file.
+ */
+
+import { useCallback, useEffect, useRef, useState } from "react";
+import { fetchParsedJailFile, updateParsedJailFile } from "../api/config";
+import type { JailFileConfig, JailFileConfigUpdate } from "../types/config";
+
+export interface UseJailFileConfigResult {
+  config: JailFileConfig | null;
+  loading: boolean;
+  error: string | null;
+  refresh: () => void;
+  save: (update: JailFileConfigUpdate) => Promise<void>;
+}
+
+/**
+ * Load one jail.d config file by filename and expose a ``save`` callback for
+ * partial updates.
+ *
+ * @param filename - Filename including extension (e.g. ``"sshd.conf"``).
+ */
+export function useJailFileConfig(filename: string): UseJailFileConfigResult {
+  const [config, setConfig] = useState<JailFileConfig | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+  const abortRef = useRef<AbortController | null>(null);
+
+  const load = useCallback((): void => {
+    abortRef.current?.abort();
+    const ctrl = new AbortController();
+    abortRef.current = ctrl;
+    setLoading(true);
+    setError(null);
+
+    fetchParsedJailFile(filename)
+      .then((data) => {
+        if (!ctrl.signal.aborted) {
+          setConfig(data);
+          setLoading(false);
+        }
+      })
+      .catch((err: unknown) => {
+        if (!ctrl.signal.aborted) {
+          setError(err instanceof Error ? err.message : "Failed to load jail file config");
+          setLoading(false);
+        }
+      });
+  }, [filename]);
+
+  useEffect(() => {
+    load();
+    return (): void => {
+      abortRef.current?.abort();
+    };
+  }, [load]);
+
+  const save = useCallback(
+    async (update: JailFileConfigUpdate): Promise<void> => {
+      try {
+        await updateParsedJailFile(filename, update);
+        // Optimistically merge updated jails into local state.
+        if (update.jails != null) {
+          setConfig((prev) =>
+            prev ? { ...prev, jails: { ...prev.jails, ...update.jails } } : prev
+          );
+        }
+      } catch (err: unknown) {
+        throw err instanceof Error ? err : new Error("Failed to save jail file config");
+      }
+    },
+    [filename]
+  );
+
+  return { config, loading, error, refresh: load, save };
+}