feat(channel): 缓存扁平化 + 网关映射集成 + 计费模式统一 + 模型限制

- 缓存重构为 O(1) 哈希结构 (pricingByGroupModel, mappingByGroupModel)
- 渠道模型映射接入网关流程 (Forward 前应用, a→b→c 映射链)
- 新增 billing_model_source 配置 (请求模型/最终模型计费)
- usage_logs 新增 channel_id, model_mapping_chain, billing_tier 字段
- 每种计费模式统一支持默认价格 + 区间定价
- 渠道模型限制开关 (restrict_models)
- 分组按平台分类展示 + 彩色图标
- 必填字段红色星号 + 模型映射 UI
- 去除模型通配符支持

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

@@ -29,7 +29,7 @@
       />
     </div>
     <p class="mt-1 text-xs text-gray-400">
-      {{ t('admin.channels.form.modelInputHint', 'Press Enter to add. Supports wildcard *.') }}
+      {{ t('admin.channels.form.modelInputHint', 'Press Enter to add, supports paste for batch import.') }}
     </p>
   </div>
 </template>

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

@@ -70,7 +70,7 @@
         <div class="mt-3 flex items-start gap-2">
           <div class="flex-1">
             <label class="text-xs font-medium text-gray-500 dark:text-gray-400">
-              {{ t('admin.channels.form.models', '模型列表') }}
+              {{ t('admin.channels.form.models', '模型列表') }} <span class="text-red-500">*</span>
             </label>
             <ModelTagInput
               :models="entry.models"
@@ -153,6 +153,17 @@
 
         <!-- Per-request mode -->
         <div v-else-if="entry.billing_mode === 'per_request'">
+          <!-- Default per-request price -->
+          <label class="mt-3 block text-xs font-medium text-gray-500 dark:text-gray-400">
+            {{ t('admin.channels.form.defaultPerRequestPrice', '默认单次价格（未命中层级时使用）') }}
+            <span class="ml-1 font-normal text-gray-400">$</span>
+          </label>
+          <div class="mt-1 w-48">
+            <input :value="entry.per_request_price" @input="emitField('per_request_price', ($event.target as HTMLInputElement).value)"
+              type="number" step="any" min="0" class="input text-sm" :placeholder="t('admin.channels.form.pricePlaceholder', '默认')" />
+          </div>
+
+          <!-- Tiers -->
           <div class="mt-3 flex items-center justify-between">
             <label class="text-xs font-medium text-gray-500 dark:text-gray-400">
               {{ t('admin.channels.form.requestTiers', '按次计费层级') }}
@@ -176,8 +187,19 @@
           </div>
         </div>
 
-        <!-- Image mode (legacy per-request) -->
+        <!-- Image mode -->
         <div v-else-if="entry.billing_mode === 'image'">
+          <!-- Default image price -->
+          <label class="mt-3 block text-xs font-medium text-gray-500 dark:text-gray-400">
+            {{ t('admin.channels.form.defaultImagePrice', '默认图片价格（未命中层级时使用）') }}
+            <span class="ml-1 font-normal text-gray-400">$</span>
+          </label>
+          <div class="mt-1 w-48">
+            <input :value="entry.image_output_price" @input="emitField('image_output_price', ($event.target as HTMLInputElement).value)"
+              type="number" step="any" min="0" class="input text-sm" :placeholder="t('admin.channels.form.pricePlaceholder', '默认')" />
+          </div>
+
+          <!-- Image tiers -->
           <div class="mt-3 flex items-center justify-between">
             <label class="text-xs font-medium text-gray-500 dark:text-gray-400">
               {{ t('admin.channels.form.imageTiers', '图片计费层级（按次）') }}
@@ -196,15 +218,6 @@
               @remove="removeInterval(idx)"
             />
           </div>
-          <div v-else>
-            <div class="mt-2 grid grid-cols-2 gap-2 sm:grid-cols-4">
-              <div>
-                <label class="text-xs text-gray-400">{{ t('admin.channels.form.imageOutputPrice', '图片输出价格') }}</label>
-                <input :value="entry.image_output_price" @input="emitField('image_output_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', '默认')" />
-              </div>
-            </div>
-          </div>
         </div>
       </div>
     </div>

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

@@ -20,6 +20,7 @@ export interface PricingFormEntry {
   cache_write_price: number | string | null
   cache_read_price: number | string | null
   image_output_price: number | string | null
+  per_request_price: number | string | null
   intervals: IntervalFormEntry[]
 }