perf(frontend): replace blank Suspense fallbacks with Spin, switch to matchMedia hook, add virtual table scrolling (#6187)

- routes.tsx, LazyMount.tsx: replace Suspense fallback={null} with Spin
  loader so page transitions and lazy modals never show blank content
- useMediaQuery.ts: switch from resize event to matchMedia change event,
  eliminating state updates on every pixel drag; export MOBILE_BREAKPOINT_PX
- SubPage.tsx: drop duplicate inline isMobile logic (7 lines), use shared
  useMediaQuery(576) (2 lines)
- ClientsPage, InboundList, HostList, NodeList: add virtual + scroll.y to
  Table for viewport-only DOM rendering of large datasets

frontend/src/pages/inbounds/list/InboundList.tsx

@@ -286,7 +286,8 @@ export default function InboundList({
               onChange: (keys: Key[]) => setSelectedRowKeys(keys as number[]),
             }}
             pagination={paginationFor(visibleInbounds)}
-            scroll={{ x: tableScrollX }}
+            scroll={{ x: tableScrollX, y: 'calc(100vh - 320px)' }}
+            virtual
             style={{ marginTop: 10 }}
             size="small"
             locale={{