fix(i18n): 补全 367 个缺失的 en-US 翻译键 — monitor 命名空间全覆盖

zh-CN/en-US 翻译键差集从 367 → 0，双语完全对齐 (6088/6088 keys)。

修复内容:
- monitor.alertChannel.* (25 keys): 通知渠道管理弹框
- monitor.alertChannels.* (13 keys): 渠道列表 Tab
- monitor.alertHelper.* (19 keys): 告警辅助函数（渠道/严重度/来源/状态）
- monitor.alertRulesTab.* (13 keys): 告警规则 Tab
- monitor.contactDialog.* (18 keys): 联系人弹框
- monitor.contactGroup.* (14 keys): 联系组弹框
- monitor.hostDashboard.* (23 keys): 主机监控仪表盘
- monitor.logPanel.* (58 keys): 日志查询面板（含 logResults 子命名空间）
- monitor.metricCatalog.* (8 keys): 指标目录
- monitor.monitorRule.* (17 keys): 监控规则配置
- monitor.notifyPolicy.* (30 keys): 通知策略
- monitor.promDs.* (17 keys): Prometheus 数据源配置
- monitor.silenceDialog.* (33 keys): 静默规则弹框
- monitor.silenceRules.* (34 keys): 静默规则列表
- monitor.traceMgr.* (35 keys): 链路追踪管理

新增 scripts/i18n-verify-keys.py 差集检测脚本 (--fix 可自动补全占位)。

⚠️ 缺失翻译键是静默失败: i18next 渲染 key 路径本身而非翻译文本,
切换到英文时用户看到 monitor.xxx.xxx 而非英文。

scripts/i18n-verify-keys.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env python3
+"""
+i18n-verify-keys.py — Detect missing/extra translation keys between zh-CN and en-US.
+
+Usage:
+    python3 scripts/i18n-verify-keys.py          # Report only
+    python3 scripts/i18n-verify-keys.py --fix     # Copy zh-CN values as placeholder
+
+Exit code: 0 if keys are in sync, 1 if there are missing keys.
+"""
+import json
+import sys
+import os
+import argparse
+
+def flatten(d, prefix=''):
+    items = {}
+    for k, v in d.items():
+        full = f'{prefix}.{k}' if prefix else k
+        if isinstance(v, dict):
+            items.update(flatten(v, full))
+        else:
+            items[full] = v
+    return items
+
+def set_nested(d, key_path, value):
+    parts = key_path.split('.')
+    current = d
+    for part in parts[:-1]:
+        if part not in current or not isinstance(current[part], dict):
+            current[part] = {}
+        current = current[part]
+    current[parts[-1]] = value
+
+def main():
+    parser = argparse.ArgumentParser(description='Verify i18n key parity between zh-CN and en-US')
+    parser.add_argument('--fix', action='store_true', help='Copy zh-CN values as placeholder for missing en-US keys')
+    args = parser.parse_args()
+
+    base = os.path.join(os.path.dirname(__file__), '..', 'frontend', 'src', 'locales')
+    zh_path = os.path.join(base, 'zh-CN.json')
+    en_path = os.path.join(base, 'en-US.json')
+
+    zh = json.load(open(zh_path))
+    en = json.load(open(en_path))
+
+    zh_flat = flatten(zh)
+    en_flat = flatten(en)
+
+    missing_en = sorted(set(zh_flat) - set(en_flat))
+    extra_en = sorted(set(en_flat) - set(zh_flat))
+
+    print(f'zh-CN keys: {len(zh_flat)}')
+    print(f'en-US keys: {len(en_flat)}')
+    print(f'Missing in en-US: {len(missing_en)}')
+    print(f'Extra in en-US:   {len(extra_en)}')
+
+    if missing_en:
+        # Group by namespace
+        ns = {}
+        for k in missing_en:
+            prefix = k.split('.')[0] + '.' + k.split('.')[1] if '.' in k else k
+            ns[prefix] = ns.get(prefix, 0) + 1
+        print('\nMissing by sub-namespace:')
+        for k, v in sorted(ns.items()):
+            print(f'  {k}.* : {v} keys')
+
+        print('\nFirst 20 missing keys:')
+        for k in missing_en[:20]:
+            print(f'  - {k} = {zh_flat[k]}')
+
+    if extra_en:
+        print('\nExtra en-US keys (not in zh-CN):')
+        for k in extra_en[:10]:
+            print(f'  + {k}')
+
+    if args.fix and missing_en:
+        for key in missing_en:
+            set_nested(en, key, zh_flat[key])
+        with open(en_path, 'w', encoding='utf-8') as f:
+            json.dump(en, f, ensure_ascii=False, indent=2)
+            f.write('\n')
+        print(f'\n[fix] Copied {len(missing_en)} zh-CN values as en-US placeholders.')
+        print('[fix] NOTE: Replace with proper English translations!')
+
+    if missing_en or extra_en:
+        sys.exit(1)
+    else:
+        print('\n✅ zh-CN and en-US keys are in sync.')
+        sys.exit(0)
+
+if __name__ == '__main__':
+    main()