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

i18n/keys.go

@@ -101,6 +101,7 @@ const (
 	MsgUserTelegramIdEmpty           = "user.telegram_id_empty"
 	MsgUserTelegramNotBound          = "user.telegram_not_bound"
 	MsgUserLinuxDOIdEmpty            = "user.linux_do_id_empty"
+	MsgUserQuotaChangeZero           = "user.quota_change_zero"
 )
 
 // Quota related messages

i18n/locales/en.yaml

@@ -91,6 +91,7 @@ user.wechat_id_empty: "WeChat ID is empty!"
 user.telegram_id_empty: "Telegram ID is empty!"
 user.telegram_not_bound: "This Telegram account is not bound"
 user.linux_do_id_empty: "Linux DO ID is empty!"
+user.quota_change_zero: "Quota change amount cannot be zero"
 
 # Quota messages
 quota.negative: "Quota cannot be negative!"

i18n/locales/zh-CN.yaml

@@ -92,6 +92,7 @@ user.wechat_id_empty: "WeChat id 为空！"
 user.telegram_id_empty: "Telegram id 为空！"
 user.telegram_not_bound: "该 Telegram 账户未绑定"
 user.linux_do_id_empty: "Linux DO id 为空！"
+user.quota_change_zero: "额度变更量不能为0"
 
 # Quota messages
 quota.negative: "额度不能为负数！"

i18n/locales/zh-TW.yaml

@@ -92,6 +92,7 @@ user.wechat_id_empty: "WeChat id 為空！"
 user.telegram_id_empty: "Telegram id 為空！"
 user.telegram_not_bound: "該 Telegram 帳號未綁定"
 user.linux_do_id_empty: "Linux DO id 為空！"
+user.quota_change_zero: "額度變更量不能為0"
 
 # Quota messages
 quota.negative: "額度不能為負數！"