♻️ Refactor: Move token unit toggle from table header to filter settings

- Remove K/M switch from model price column header in pricing table
- Add "Display in K units" option to pricing display settings panel
- Update parameter passing for tokenUnit and setTokenUnit across components:
  - PricingDisplaySettings: Add tokenUnit toggle functionality
  - PricingSidebar: Pass tokenUnit props to display settings
  - PricingFilterModal: Include tokenUnit in mobile filter modal
- Enhance resetPricingFilters utility to reset token unit to default 'M'
- Clean up PricingTableColumns by removing unused setTokenUnit parameter
- Add English translation for "按K显示单位" as "Display in K units"

This change improves UX by consolidating all display-related controls
in the filter settings panel, making the interface more organized and
the token unit setting more discoverable alongside other display options.

Affected components:
- PricingTableColumns.js
- PricingDisplaySettings.jsx
- PricingSidebar.jsx
- PricingFilterModal.jsx
- PricingTable.jsx
- utils.js (resetPricingFilters)
- en.json (translations)

web/src/hooks/common/useMinimumLoadingTime.js

@@ -0,0 +1,50 @@
+/*
+Copyright (C) 2025 QuantumNous
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+For commercial licensing, please contact support@quantumnous.com
+*/
+
+import { useState, useEffect, useRef } from 'react';
+
+/**
+ * 自定义 Hook：确保骨架屏至少显示指定的时间
+ * @param {boolean} loading - 实际的加载状态
+ * @param {number} minimumTime - 最小显示时间（毫秒），默认 1000ms
+ * @returns {boolean} showSkeleton - 是否显示骨架屏的状态
+ */
+export const useMinimumLoadingTime = (loading, minimumTime = 1000) => {
+  const [showSkeleton, setShowSkeleton] = useState(loading);
+  const loadingStartRef = useRef(Date.now());
+
+  useEffect(() => {
+    if (loading) {
+      loadingStartRef.current = Date.now();
+      setShowSkeleton(true);
+    } else {
+      const elapsed = Date.now() - loadingStartRef.current;
+      const remaining = Math.max(0, minimumTime - elapsed);
+
+      if (remaining === 0) {
+        setShowSkeleton(false);
+      } else {
+        const timer = setTimeout(() => setShowSkeleton(false), remaining);
+        return () => clearTimeout(timer);
+      }
+    }
+  }, [loading, minimumTime]);
+
+  return showSkeleton;
+};