refactor: Remove unused preview actions from ASNs, Domains, and IPRanges managers; streamline PageHeaderActions component for improved clarity and usability

frontend/src/ASNsNewManager.jsx

@@ -15,8 +15,7 @@ import {
   IconDeviceFloppy,
   IconHash,
   IconClock,
-  IconFileText,
-  IconEye
+  IconFileText
 } from '@tabler/icons-react';
 import LockBanner from './components/LockBanner.jsx';
 import TableSkeleton from './components/TableSkeleton.jsx';
@@ -399,8 +398,6 @@ function ASNsNewManager() {
           <div className="col-auto ms-auto d-print-none">
             <PageHeaderActions
               loading={loading}
-              onPreview={handlePreviewDiff}
-              disablePreview={loading || items.length === 0}
               onRefresh={fetchItems}
               disableRefresh={loading}
               onImport={handleImport}

frontend/src/DomainsNewManager.jsx

@@ -15,8 +15,7 @@ import {
   IconDeviceFloppy,
   IconHash,
   IconClock,
-  IconFileText,
-  IconEye
+  IconFileText
 } from '@tabler/icons-react';
 import LockBanner from './components/LockBanner.jsx';
 import TableSkeleton from './components/TableSkeleton.jsx';
@@ -406,8 +405,6 @@ function DomainsNewManager() {
           <div className="col-auto ms-auto d-print-none">
             <PageHeaderActions
               loading={loading}
-              onPreview={handlePreviewDiff}
-              disablePreview={loading || items.length === 0}
               onRefresh={fetchItems}
               disableRefresh={loading}
               onImport={handleImport}

frontend/src/IPRangesManager.jsx

@@ -15,8 +15,7 @@ import {
   IconDeviceFloppy,
   IconHash,
   IconClock,
-  IconFileText,
-  IconEye
+  IconFileText
 } from '@tabler/icons-react';
 import LockBanner from './components/LockBanner.jsx';
 import TableSkeleton from './components/TableSkeleton.jsx';
@@ -415,8 +414,6 @@ function IPRangesManager() {
           <div className="col-auto ms-auto d-print-none">
             <PageHeaderActions
               loading={loading}
-              onPreview={handlePreviewDiff}
-              disablePreview={loading || items.length === 0}
               onRefresh={fetchItems}
               disableRefresh={loading}
               onImport={handleImport}

frontend/src/components/PageHeaderActions.jsx

@@ -1,5 +1,4 @@
 import { 
-  IconEye,
   IconRefresh,
   IconUpload,
   IconDownload,
@@ -28,38 +27,58 @@ function PageHeaderActions({
   return (
     <div className="header-actions" role="toolbar" aria-label="Действия страницы">
       <div className="btn-group">
-        {onOnlineUpdate && (
-          <button className="btn btn-outline-warning" type="button" onClick={onOnlineUpdate} title="Online-обновление BGP (WebSocket)">
-            <IconBolt className="me-1" /> Online-обновление
-          </button>
-        )}
-        {onBackgroundUpdate && (
-          <button className="btn btn-outline-success" type="button" onClick={onBackgroundUpdate} title="Фоновое обновление BGP (POST)">
-            <IconPlayerPlay className="me-1" /> Фоновое обновление
-          </button>
+        {(onBackgroundUpdate || onOnlineUpdate) && (
+          <div className="btn-group">
+            {/* Дефолтное действие — фоновое обновление */}
+            <button 
+              className="btn btn-outline-success" 
+              type="button" 
+              onClick={onBackgroundUpdate || onOnlineUpdate}
+              title="Фоновое обновление BGP (POST)"
+            >
+              <IconPlayerPlay className="me-1" /> Фоновое обновление
+            </button>
+            {(onBackgroundUpdate && onOnlineUpdate) && (
+              <>
+                <button className="btn btn-outline-success dropdown-toggle dropdown-toggle-split" type="button" data-bs-toggle="dropdown" aria-expanded="false" aria-label="Другие варианты обновления"></button>
+                <div className="dropdown-menu">
+                  <button className="dropdown-item" type="button" onClick={onBackgroundUpdate}>
+                    <IconPlayerPlay className="me-1" /> Фоновое обновление
+                  </button>
+                  <button className="dropdown-item" type="button" onClick={onOnlineUpdate}>
+                    <IconBolt className="me-1" /> Online-обновление
+                  </button>
+                </div>
+              </>
+            )}
+          </div>
         )}
       </div>
       <span className="vr d-none d-lg-inline" />
       <div className="btn-group">
-        {onPreview && (
-          <button className="btn btn-outline-secondary" type="button" onClick={onPreview} disabled={disablePreview} title="Предпросмотр изменений">
-            <IconEye className="me-1" /> Предпросмотр
-          </button>
-        )}
         {onRefresh && (
           <button className="btn btn-outline-secondary" type="button" onClick={onRefresh} disabled={disableRefresh} title="Обновить данные">
             <IconRefresh className={loading ? 'spin me-1' : 'me-1'} /> Обновить
           </button>
         )}
-        {onImport && (
-          <button className="btn btn-outline-primary" type="button" onClick={onImport} title="Импорт">
-            <IconUpload className="me-1" /> Импорт
-          </button>
-        )}
-        {onExport && (
-          <button className="btn btn-outline-primary" type="button" onClick={onExport} disabled={disableExport} title="Экспорт">
-            <IconDownload className="me-1" /> Экспорт
-          </button>
+        {(onImport || onExport) && (
+          <div className="dropdown">
+            <button className="btn btn-outline-primary dropdown-toggle" type="button" data-bs-toggle="dropdown" aria-expanded="false" title="Импорт/Экспорт">
+              <IconDownload className="me-1" /> Импорт/Экспорт
+            </button>
+            <div className="dropdown-menu">
+              {onImport && (
+                <button className="dropdown-item" type="button" onClick={onImport}>
+                  <IconUpload className="me-1" /> Импорт
+                </button>
+              )}
+              {onExport && (
+                <button className="dropdown-item" type="button" onClick={onExport} disabled={disableExport}>
+                  <IconDownload className="me-1" /> Экспорт
+                </button>
+              )}
+            </div>
+          </div>
         )}
         {onClear && (
           <button className="btn btn-outline-secondary" type="button" onClick={onClear} disabled={disableClear} title="Очистить пустые/невалидные">