fix: change quota notify threshold semantics to "remaining quota"

Threshold now represents remaining quota instead of usage amount:
- Fixed ($): threshold=400, limit=1000 → alert when remaining drops to $400
  (i.e., usage reaches $600)
- Percentage (%): threshold=30%, limit=1000 → alert when remaining drops
  to 30% (i.e., usage reaches $700)

Also:
- Rename 告警阈值 → 提醒阈值 in i18n
- Widen type dropdown to w-16 for proper $ / % display

backend/cmd/server/VERSION

@@ -1 +1 @@
-0.1.110.33
+0.1.110.34

backend/internal/service/balance_notify_service.go

@@ -137,13 +137,18 @@ type quotaDim struct {
 	limit         float64
 }
 
-// resolvedThreshold returns the effective threshold value.
-// For percentage type, it computes threshold = limit * percentage / 100.
+// resolvedThreshold converts the user-facing "remaining" threshold into a usage-based trigger point.
+// The threshold represents how much quota REMAINS when the alert fires:
+//   - Fixed ($): threshold=400, limit=1000 → fires when usage reaches 600 (remaining drops to 400)
+//   - Percentage (%): threshold=30, limit=1000 → fires when usage reaches 700 (remaining drops to 30%)
 func (d quotaDim) resolvedThreshold() float64 {
-	if d.thresholdType == thresholdTypePercentage && d.limit > 0 {
-		return d.limit * d.threshold / 100
+	if d.limit <= 0 {
+		return 0
 	}
-	return d.threshold
+	if d.thresholdType == thresholdTypePercentage {
+		return d.limit * (1 - d.threshold/100)
+	}
+	return d.limit - d.threshold
 }
 
 // buildQuotaDims returns the three quota dimensions for notification checking.

frontend/src/components/account/QuotaNotifyToggle.vue

@@ -42,7 +42,7 @@ const emit = defineEmits<{
       <select
         :value="thresholdType || 'fixed'"
         @change="emit('update:thresholdType', ($event.target as HTMLSelectElement).value)"
-        class="input py-1 text-xs w-14 flex-shrink-0 text-center appearance-auto"
+        class="input py-1 text-xs w-16 flex-shrink-0 text-center"
       >
         <option value="fixed">$</option>
         <option value="percentage">%</option>

frontend/src/i18n/locales/en.ts

@@ -2243,7 +2243,7 @@ export default {
       quotaLimitAmount: 'Total Limit',
       quotaLimitAmountHint: 'Cumulative spending limit. Does not auto-reset.',
       quotaNotify: {
-        alert: 'Alert Threshold',
+        alert: 'Alert',
         enabled: 'Enable Alert',
         threshold: 'Alert Amount',
         thresholdPlaceholder: 'Enter percentage',

frontend/src/i18n/locales/zh.ts

@@ -2249,7 +2249,7 @@ export default {
       quotaLimitAmount: '总限额',
       quotaLimitAmountHint: '累计消费上限，不会自动重置。',
       quotaNotify: {
-        alert: '告警阈值',
+        alert: '提醒阈值',
         enabled: '启用告警',
         threshold: '告警金额',
         thresholdPlaceholder: '输入百分比',