chore(ui): polish empty states + sidebar icon + i18n page titles

- AppSidebar: switch the inbounds icon from UserOutlined (a single
  person — wrong semantic) to ImportOutlined, matching the empty-state
  icon and reflecting the actual concept of an incoming entry point.
- usePageTitle: stop hardcoding English titles; resolve them through
  i18n (menu.* keys are already translated), so the browser tab now
  follows the active language.
- InboundList / NodeList: replace the bare "—" empty cell with a
  centered icon + t('noData') message (ImportOutlined for inbounds,
  ClusterOutlined for nodes), and swap opacity:0.4 for
  var(--ant-color-text-secondary) so the text stays readable on the
  light theme's tinted card background.

frontend/src/pages/inbounds/InboundList.css

@@ -132,8 +132,12 @@
 
 .card-empty {
   text-align: center;
-  opacity: 0.4;
-  padding: 20px 0;
+  color: var(--ant-color-text-secondary);
+  padding: 24px 12px;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 8px;
 }
 
 @media (max-width: 768px) {

frontend/src/pages/inbounds/InboundList.tsx

@@ -600,7 +600,10 @@ export default function InboundList({
         {isMobile ? (
           <div className="inbound-cards">
             {sortedInbounds.length === 0 ? (
-              <div className="card-empty">—</div>
+              <div className="card-empty">
+                <ImportOutlined style={{ fontSize: 28, opacity: 0.5 }} />
+                <div>{t('noData')}</div>
+              </div>
             ) : (
               sortedInbounds.map((record) => (
                 <div key={record.id} className="inbound-card">
@@ -641,6 +644,14 @@ export default function InboundList({
             scroll={{ x: 1000 }}
             style={{ marginTop: 10 }}
             size="small"
+            locale={{
+              emptyText: (
+                <div className="card-empty">
+                  <ImportOutlined style={{ fontSize: 32, marginBottom: 8 }} />
+                  <div>{t('noData')}</div>
+                </div>
+              ),
+            }}
             onChange={(_p, _f, sorter) => {
               const single = Array.isArray(sorter) ? sorter[0] : sorter;
               const colKey = (single?.columnKey || single?.field) as SortKey | undefined;

frontend/src/pages/nodes/NodeList.css

@@ -135,6 +135,10 @@
 
 .card-empty {
   text-align: center;
-  opacity: 0.4;
-  padding: 20px 0;
+  color: var(--ant-color-text-secondary);
+  padding: 24px 12px;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 8px;
 }

frontend/src/pages/nodes/NodeList.tsx

@@ -15,6 +15,7 @@ import {
 import type { BadgeProps } from 'antd';
 import type { ColumnsType } from 'antd/es/table';
 import {
+  ClusterOutlined,
   DeleteOutlined,
   EditOutlined,
   ExclamationCircleOutlined,
@@ -279,7 +280,10 @@ export default function NodeList({
         <>
           <div className="node-cards">
             {dataSource.length === 0 ? (
-              <div className="card-empty">—</div>
+              <div className="card-empty">
+                <ClusterOutlined style={{ fontSize: 28, opacity: 0.5 }} />
+                <div>{t('noData')}</div>
+              </div>
             ) : (
               dataSource.map((record) => (
                 <div key={record.id} className="node-card">
@@ -435,6 +439,14 @@ export default function NodeList({
           scroll={{ x: 'max-content' }}
           size="middle"
           rowKey="id"
+          locale={{
+            emptyText: (
+              <div className="card-empty">
+                <ClusterOutlined style={{ fontSize: 32, marginBottom: 8 }} />
+                <div>{t('noData')}</div>
+              </div>
+            ),
+          }}
           expandable={{
             expandedRowRender: (record) => <NodeHistoryPanel node={record} />,
           }}