feat: add AI Credits balance handling and update model status indicators

frontend/src/types/index.ts

@@ -664,6 +664,7 @@ export interface Account {
   // Extra fields including Codex usage and model-level rate limits (Antigravity smart retry)
   extra?: (CodexUsageSnapshot & {
     model_rate_limits?: Record<string, { rate_limited_at: string; rate_limit_reset_at: string }>
+    antigravity_credits_overages?: Record<string, { activated_at: string; active_until: string }>
   } & Record<string, unknown>)
   proxy_id: number | null
   concurrency: number
@@ -780,6 +781,11 @@ export interface AccountUsageInfo {
   gemini_pro_minute?: UsageProgress | null
   gemini_flash_minute?: UsageProgress | null
   antigravity_quota?: Record<string, AntigravityModelQuota> | null
+  ai_credits?: Array<{
+    credit_type?: string
+    amount?: number
+    minimum_balance?: number
+  }> | null
   // Antigravity 403 forbidden 状态
   is_forbidden?: boolean
   forbidden_reason?: string