feat: replace quota input with amount-first UI and atomic quota adjustment

- Refactor token, redemption, and user quota inputs to prioritize monetary
  amount entry, with raw quota input collapsed by default
- Add atomic quota adjustment modal for users with add/subtract/override modes,
  bypassing batch update queue for immediate DB consistency
- Make user quota fields readonly in edit form; all modifications go through
  the dedicated adjust-quota modal via POST /api/user/manage
- Add DecreaseUserQuota `db` parameter for direct DB writes, matching
  IncreaseUserQuota behavior
- Support negative quota display in amount conversion helpers
- Add i18n keys for all new UI strings across all locales

web/src/i18n/locales/en.json

@@ -825,6 +825,8 @@
     "原密码": "Original Password",
     "原生格式": "Native format",
     "原生额度": "Raw quota",
+    "使用原生额度输入": "Use raw quota input",
+    "收起原生额度输入": "Hide raw quota input",
     "去重完成：去重前 {{before}} 个密钥，去重后 {{after}} 个密钥": "Deduplication completed: {{before}} keys before deduplication, {{after}} keys after deduplication",
     "参与官方同步": "Participate in official sync",
     "参数": "parameter",
@@ -2166,6 +2168,14 @@
     "添加键值对": "Add key-value pair",
     "添加问答": "Add FAQ",
     "添加额度": "Add quota",
+    "减少": "Subtract",
+    "覆盖": "Override",
+    "调整额度": "Adjust Quota",
+    "调整额度成功": "Quota adjusted successfully",
+    "当前额度": "Current quota",
+    "变更": "Change",
+    "预计结果": "Estimated result",
+    "正数为增加，负数为减少": "Positive to add, negative to subtract",
     "清理不活跃缓存": "Clean up inactive cache",
     "清理失败": "Cleanup failed",
     "清理方式": "Cleanup Mode",