feat: add OpenAI image generation controls

frontend/src/i18n/locales/en.ts

@@ -844,6 +844,8 @@ export default {
     perMillionTokens: '/ 1M tokens',
     unitPrice: 'Per-request price',
     imageUnitPrice: 'Per-image price',
+    imageTotalPrice: 'Image total price',
+    imageCount: 'Image count',
     cacheRead: 'Read',
     cacheWrite: 'Write',
     serviceTier: 'Service tier',
@@ -2050,7 +2052,13 @@ export default {
       },
       imagePricing: {
         title: 'Image Generation Pricing',
-        description: 'Configure pricing for image generation models. Leave empty to use default prices.'
+        description: 'Configure image generation access and base image prices. Leave empty to use default prices.',
+        allowImageGeneration: 'Allow image generation for this group',
+        independentMultiplier: 'Use independent image multiplier',
+        imageMultiplier: 'Image multiplier',
+        modeHint: 'By default, image billing uses image price × current effective group multiplier. Independent mode uses image price × image multiplier.',
+        finalPricePreview: 'Final per-image price preview',
+        notConfigured: 'Not configured'
       },
       claudeCode: {
         title: 'Claude Code Client Restriction',

frontend/src/i18n/locales/zh.ts

@@ -848,6 +848,8 @@ export default {
     perMillionTokens: '/ 1M Token',
     unitPrice: '单次价格',
     imageUnitPrice: '单张价格',
+    imageTotalPrice: '图片总价',
+    imageCount: '图片张数',
     cacheRead: '读取',
     cacheWrite: '写入',
     serviceTier: '服务档位',
@@ -2133,7 +2135,13 @@ export default {
       },
       imagePricing: {
         title: '图片生成计费',
-        description: '配置图片生成模型的图片生成价格，留空则使用默认价格'
+        description: '配置图片生成能力和图片基础单价，留空则使用默认价格',
+        allowImageGeneration: '允许当前分组生图',
+        independentMultiplier: '生图倍率独立',
+        imageMultiplier: '生图独立倍率',
+        modeHint: '默认关闭独立倍率时，图片费用 = 图片价格 × 当前分组有效倍率；开启独立倍率后，图片费用 = 图片价格 × 生图独立倍率。',
+        finalPricePreview: '最终单张价格预览',
+        notConfigured: '未配置'
       },
       claudeCode: {
         title: 'Claude Code 客户端限制',