GitLab

- Fix gofmt alignment in setting_handler.go, settings.go, payment_config_service.go
- Add payment_balance_recharge_multiplier and payment_recharge_fee_rate
  to API contract test expected JSON

- Add recharge_fee_rate system setting (percentage fee on top of recharge amount)
- Full backend chain: config constant, PaymentConfig struct, update validation,
  read/write persistence, DTO, handler GET/PUT responses
- Frontend: settings input with preview, i18n (zh/en), API types
- Fix provider card toggle layout: labels above switches to save width
- Fix Chinese translation: "EasyPay" → "易支付" in provider description

- Add balance_recharge_multiplier system setting (e.g. 1.2 = charge 100 get 120)
- Separate order_amount (credited balance) from pay_amount (actual payment)
- Refund calculates gateway amount proportionally from pay_amount
- Frontend shows both amounts in order details, payment status, refund dialog
- Admin settings UI for configuring recharge multiplier

- Refactor OpenAI Messages() routing: pre-compute dispatch model using
  resolveOpenAIMessagesDispatchMappedModel + NormalizeOpenAICompatRequestedModel
  instead of try-fail-retry pattern with gin context passing
- Remove openai_messages_fallback_model context anti-pattern
- Use effectiveMappedModel directly for forward default mapped model
- Add 3 subscription group tests covering all branch paths:
  _Blocked (no active subscription → SUBSCRIPTION_REQUIRED),
  _RequiresRepo (nil repo → SUBSCRIPTION_REPOSITORY_UNAVAILABLE),
  _AllowsActiveSubscription (valid subscription → success)