feat: add quota limit for API key accounts

- Add configurable spending limit (quota_limit) for apikey-type accounts
- Atomic quota accumulation via PostgreSQL JSONB operations on TotalCost
- Scheduler filters out over-quota accounts with outbox-triggered snapshot refresh
- Display quota usage ($used / $limit) in account capacity column
- Add "Reset Quota" action in account menu to reset usage to zero
- Editing account settings preserves quota_used (no accidental reset)
- Covers all 3 billing paths: Anthropic, Gemini, OpenAI RecordUsage

chore: bump version to 0.1.90.4

backend/internal/service/gemini_multiplatform_test.go

@@ -176,6 +176,14 @@ func (m *mockAccountRepoForGemini) BulkUpdate(ctx context.Context, ids []int64,
 	return 0, nil
 }
 
+func (m *mockAccountRepoForGemini) IncrementQuotaUsed(ctx context.Context, id int64, amount float64) error {
+	return nil
+}
+
+func (m *mockAccountRepoForGemini) ResetQuotaUsed(ctx context.Context, id int64) error {
+	return nil
+}
+
 // Verify interface implementation
 var _ AccountRepository = (*mockAccountRepoForGemini)(nil)