refactor(hooks): share floating action-bar height syncing

AuthFilesPage and ConfigPage duplicated the ResizeObserver-to-CSS-variable wiring for their bottom action bars; extract useActionBarHeightVar and use it in both.

src/hooks/useActionBarHeightVar.ts

@@ -0,0 +1,38 @@
+import { useLayoutEffect, type RefObject } from 'react';
+
+/**
+ * 将悬浮操作条的实时高度同步到根元素 CSS 变量，供页面底部留白使用。
+ * active 为 false 或元素未挂载时清除变量。
+ */
+export function useActionBarHeightVar(
+  ref: RefObject<HTMLElement | null>,
+  cssVar: string,
+  active: boolean
+) {
+  useLayoutEffect(() => {
+    if (typeof window === 'undefined') return;
+
+    const actionsEl = active ? ref.current : null;
+    if (!actionsEl) {
+      document.documentElement.style.removeProperty(cssVar);
+      return;
+    }
+
+    const updateHeight = () => {
+      const height = actionsEl.getBoundingClientRect().height;
+      document.documentElement.style.setProperty(cssVar, `${height}px`);
+    };
+
+    updateHeight();
+    window.addEventListener('resize', updateHeight);
+
+    const ro = typeof ResizeObserver === 'undefined' ? null : new ResizeObserver(updateHeight);
+    ro?.observe(actionsEl);
+
+    return () => {
+      ro?.disconnect();
+      window.removeEventListener('resize', updateHeight);
+      document.documentElement.style.removeProperty(cssVar);
+    };
+  }, [ref, cssVar, active]);
+}

src/pages/AuthFilesPage.tsx

@@ -15,6 +15,7 @@ import { animate } from 'motion/mini';
 import type { AnimationPlaybackControlsWithThen } from 'motion-dom';
 import { useInterval } from '@/hooks/useInterval';
 import { useHeaderRefresh } from '@/hooks/useHeaderRefresh';
+import { useActionBarHeightVar } from '@/hooks/useActionBarHeightVar';
 import { usePageTransitionLayer } from '@/components/common/PageTransitionLayer';
 import { Card } from '@/components/ui/Card';
 import { Button } from '@/components/ui/Button';
@@ -492,32 +493,11 @@ export function AuthFilesPage() {
     [filter, navigate]
   );
 
-  useLayoutEffect(() => {
-    if (typeof window === 'undefined') return;
-
-    const actionsEl = floatingBatchActionsRef.current;
-    if (!actionsEl) {
-      document.documentElement.style.removeProperty('--auth-files-action-bar-height');
-      return;
-    }
-
-    const updatePadding = () => {
-      const height = actionsEl.getBoundingClientRect().height;
-      document.documentElement.style.setProperty('--auth-files-action-bar-height', `${height}px`);
-    };
-
-    updatePadding();
-    window.addEventListener('resize', updatePadding);
-
-    const ro = typeof ResizeObserver === 'undefined' ? null : new ResizeObserver(updatePadding);
-    ro?.observe(actionsEl);
-
-    return () => {
-      ro?.disconnect();
-      window.removeEventListener('resize', updatePadding);
-      document.documentElement.style.removeProperty('--auth-files-action-bar-height');
-    };
-  }, [batchActionBarVisible, selectionCount]);
+  useActionBarHeightVar(
+    floatingBatchActionsRef,
+    '--auth-files-action-bar-height',
+    batchActionBarVisible
+  );
 
   useEffect(() => {
     selectionCountRef.current = selectionCount;

src/pages/ConfigPage.tsx

@@ -3,7 +3,6 @@ import {
   lazy,
   useCallback,
   useEffect,
-  useLayoutEffect,
   useMemo,
   useRef,
   useState,
@@ -25,6 +24,7 @@ import {
 import { VisualConfigEditor } from '@/components/config/VisualConfigEditor';
 import { DiffModal } from '@/components/config/DiffModal';
 import { useMediaQuery } from '@/hooks/useMediaQuery';
+import { useActionBarHeightVar } from '@/hooks/useActionBarHeightVar';
 import { useUnsavedChangesGuard } from '@/hooks/useUnsavedChangesGuard';
 import { useVisualConfig } from '@/hooks/useVisualConfig';
 import { useNotificationStore, useAuthStore, useThemeStore, useConfigStore } from '@/stores';
@@ -427,29 +427,7 @@ export function ConfigPage() {
   }, [lastSearchedQuery, performSearch]);
 
   // Keep bottom floating actions from covering page content by syncing its height to a CSS variable.
-  useLayoutEffect(() => {
-    if (typeof window === 'undefined' || !shouldRenderFloatingActions) return;
-
-    const actionsEl = floatingActionsRef.current;
-    if (!actionsEl) return;
-
-    const updatePadding = () => {
-      const height = actionsEl.getBoundingClientRect().height;
-      document.documentElement.style.setProperty('--config-action-bar-height', `${height}px`);
-    };
-
-    updatePadding();
-    window.addEventListener('resize', updatePadding);
-
-    const ro = typeof ResizeObserver === 'undefined' ? null : new ResizeObserver(updatePadding);
-    ro?.observe(actionsEl);
-
-    return () => {
-      ro?.disconnect();
-      window.removeEventListener('resize', updatePadding);
-      document.documentElement.style.removeProperty('--config-action-bar-height');
-    };
-  }, [shouldRenderFloatingActions]);
+  useActionBarHeightVar(floatingActionsRef, '--config-action-bar-height', shouldRenderFloatingActions);
 
   // Status text
   const getStatusText = () => {