feat(billing): 渠道自定义定价支持图片输入 token 单价 image_input_price

渠道 token 计费模式此前无法为图片输入 token 单独定价，gpt-image-2
图片编辑等请求的图像输入被按文本 input_price 计费。新增
channel_model_pricing.image_input_price 列及全链路支持。

后端:
- 迁移 178：channel_model_pricing 新增 image_input_price 列
- ChannelModelPricing 新增 ImageInputPrice 字段，repo 读写、校验补齐
- model_pricing_resolver / GetModelPricingWithChannel 映射到
  ImageInputPricePerToken；未配置时归零，由 computeTokenBreakdown
  回退文本输入价（向后兼容，与 image_output_price 的渠道权威规则一致）
- admin / 用户侧定价 DTO 与 model-pricing 自动填充接口补充该字段

前端:
- 渠道定价表单新增「图片输入」价格输入（token 模式）
- API 类型、表单模型、form↔API 换算、自动填充、用户侧模型定价卡展示
- zh/en i18n 标签

相关 #4386。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015wcJTKDddxXSQrepSs3wrU

frontend/src/components/admin/channel/PricingEntryCard.vue

@@ -101,7 +101,7 @@
             {{ t('admin.channels.form.defaultPrices') }}
             <span class="ml-1 font-normal text-gray-400">$/MTok</span>
           </label>
-          <div class="mt-1 grid grid-cols-2 gap-2 sm:grid-cols-5">
+          <div class="mt-1 grid grid-cols-2 gap-2 sm:grid-cols-6">
             <div>
               <label class="text-xs text-gray-400">{{ t('admin.channels.form.inputPrice') }}</label>
               <input :value="entry.input_price" @input="emitField('input_price', ($event.target as HTMLInputElement).value)"
@@ -122,6 +122,11 @@
               <input :value="entry.cache_read_price" @input="emitField('cache_read_price', ($event.target as HTMLInputElement).value)"
                 type="number" step="any" min="0" class="input mt-0.5 text-sm" :placeholder="t('admin.channels.form.pricePlaceholder')" />
             </div>
+            <div>
+              <label class="text-xs text-gray-400">{{ t('admin.channels.form.imageInputPrice') }}</label>
+              <input :value="entry.image_input_price" @input="emitField('image_input_price', ($event.target as HTMLInputElement).value)"
+                type="number" step="any" min="0" class="input mt-0.5 text-sm" :placeholder="t('admin.channels.form.pricePlaceholder')" />
+            </div>
             <div>
               <label class="text-xs text-gray-400">{{ t('admin.channels.form.imageTokenPrice') }}</label>
               <input :value="entry.image_output_price" @input="emitField('image_output_price', ($event.target as HTMLInputElement).value)"
@@ -328,6 +333,7 @@ async function onModelsUpdate(newModels: string[]) {
         output_price: perTokenToMTok(result.output_price ?? null),
         cache_write_price: perTokenToMTok(result.cache_write_price ?? null),
         cache_read_price: perTokenToMTok(result.cache_read_price ?? null),
+        image_input_price: perTokenToMTok(result.image_input_price ?? null),
         image_output_price: perTokenToMTok(result.image_output_price ?? null),
       })
     }

frontend/src/components/admin/channel/types.ts

@@ -21,6 +21,7 @@ export interface PricingFormEntry {
   output_price: number | string | null
   cache_write_price: number | string | null
   cache_read_price: number | string | null
+  image_input_price: number | string | null
   image_output_price: number | string | null
   per_request_price: number | string | null
   intervals: IntervalFormEntry[]

frontend/src/components/channels/SupportedModelChip.vue

@@ -90,6 +90,13 @@
                 :unit="t(prefixKey('unitPerMillion'))"
                 :scale="perMillionScale"
               />
+              <PricingRow
+                v-if="model.pricing.image_input_price != null && model.pricing.image_input_price > 0"
+                :label="t(prefixKey('imageInputPrice'))"
+                :value="model.pricing.image_input_price"
+                :unit="t(prefixKey('unitPerMillion'))"
+                :scale="perMillionScale"
+              />
               <PricingRow
                 v-if="model.pricing.image_output_price != null && model.pricing.image_output_price > 0"
                 :label="t(prefixKey('imageOutputPrice'))"