feat: 数据脱敏体系重构 — 全局设置+masked_columns+前端去硬编码

后端:
- applyDataMasking 新增 masked_columns 返回字段，告诉前端哪些列被脱敏
- seedDefaultSettings 添加 data_masking 分组(启用开关+敏感字段列表)
- 脱敏逻辑: 全局敏感字段 + 实例级 mask_fields 合并，开关关闭则跳过

前端:
- QueriesPage 去掉硬编码 sensitiveKeywords 和 maskData()
- 改用后端返回的 masked_columns 显示'敏'标签
- 脱敏值由后端统一处理(替换为*)
- PlatformConfigPage 数据脱敏分组独立显示
- EditInstanceDialog 脱敏字段简化为逗号分隔输入

验证:
- 设置页开关可正常开关/保存
- 查询 ghost_test: email列被脱敏为*，列头显示'敏'标签
- 非敏感列(name, id, status)正常显示

frontend/src/pages/QueriesPage.tsx

@@ -32,6 +32,7 @@ interface QueryResult {
   raw_key?: string;
   raw_text?: string;
   error?: string;
+  masked_columns?: string[];
 }
 
 interface QueryHistoryItem {
@@ -64,7 +65,8 @@ const dbTypeIcon: Record<string, string> = {
   mongodb: '/db-logos/mongo.svg',
 };
 
-const sensitiveKeywords = ['password', 'pwd', 'secret', 'token', 'phone', 'mobile', 'email', 'id_card', 'card_no'];
+// 脱敏关键词不再硬编码——由后端 applyDataMasking 返回 masked_columns 标记
+// 后端根据 data_masking_enabled + data_masking_sensitive_fields + 实例 mask_fields 决定
 
 const placeholderMap: Record<DBType, string> = {
   mysql: "-- MySQL 查询\n-- 仅支持 SELECT, SHOW, EXPLAIN, DESCRIBE\n\nSELECT id, name, status\nFROM users\nWHERE status = 'active'\nLIMIT 100;",
@@ -76,16 +78,6 @@ const placeholderMap: Record<DBType, string> = {
 /* ------------------------------------------------------------------ */
 /*  Helpers                                                            */
 /* ------------------------------------------------------------------ */
-function maskData(value: string): string {
-  if (!value) return '***';
-  if (typeof value === 'string' && value.includes('@')) {
-    const [name, domain] = value.split('@');
-    return name.substring(0, 3) + '***@' + domain;
-  }
-  if (typeof value === 'string' && value.length > 7) return value.substring(0, 3) + '****' + value.substring(value.length - 4);
-  return '***';
-}
-
 function exportToCSV(columns: string[], rows: Record<string, unknown>[]): string {
   const header = columns.join(',');
   const lines = rows.map(row =>
@@ -534,7 +526,7 @@ export default function QueriesPage() {
                             className="text-left px-3 py-2 font-semibold text-xs cursor-pointer hover:text-blue-400 transition-colors select-none whitespace-nowrap">
                             <div className="flex items-center gap-1">
                               {col} <SortIcon col={col} />
-                              {sensitiveKeywords.some(k => col.toLowerCase().includes(k)) && (
+                              {result.masked_columns?.includes(col) && (
                                 <span className="ml-1 px-1 py-0.5 bg-yellow-500/10 text-yellow-400 text-[9px] rounded">敏</span>
                               )}
                             </div>
@@ -550,12 +542,12 @@ export default function QueriesPage() {
                           <tr key={ri} className="dg-table-row" style={{ height: rowHeight }}>
                             <td className="px-3 py-2 text-[10px] text-[var(--dg-text-muted)] font-mono">{ri + 1}</td>
                             {result.columns.map(col => {
-                              const isSensitive = sensitiveKeywords.some(k => col.toLowerCase().includes(k));
+                              const isMasked = result.masked_columns?.includes(col);
                               const cellValue = row[col] ?? '';
                               const { text: displayText, isJson } = formatCellValue(cellValue);
                               return (
                                 <td key={col} className={`px-3 py-2 text-xs ${isJson ? 'max-w-[500px] whitespace-pre-wrap break-all font-mono text-[11px] leading-relaxed' : 'whitespace-pre-wrap break-words'}`} title={String(cellValue)}>
-                                  {isSensitive ? <span className="text-yellow-400 italic">{maskData(String(cellValue))}</span> :
+                                  {isMasked ? <span className="text-yellow-400 italic">{String(cellValue)}</span> :
                                    isJson ? <span className="text-blue-300">{displayText}</span> :
                                    String(cellValue)}
                                 </td>