feat(openai): add /v1/messages endpoint and API compatibility layer

Add Anthropic Messages API support for OpenAI platform groups, enabling
clients using Claude-style /v1/messages format to access OpenAI accounts
through automatic protocol conversion.

- Add apicompat package with type definitions and bidirectional converters
  (Anthropic ↔ Chat, Chat ↔ Responses, Anthropic ↔ Responses)
- Implement /v1/messages endpoint for OpenAI gateway with streaming support
- Add model mapping UI for OpenAI OAuth accounts (whitelist + mapping modes)
- Support prompt caching fields and codex OAuth transforms
- Fix tool call ID conversion for Responses API (fc_ prefix)
- Ensure function_call_output has non-empty output field

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/account/CreateAccountModal.vue

@@ -1230,6 +1230,142 @@
       <!-- API Key 账号配额限制 -->
       <QuotaLimitCard v-if="form.type === 'apikey'" v-model="editQuotaLimit" />
 
+      <!-- OpenAI OAuth Model Mapping (OAuth 类型没有 apikey 容器，需要独立的模型映射区域) -->
+      <div
+        v-if="form.platform === 'openai' && accountCategory === 'oauth-based'"
+        class="border-t border-gray-200 pt-4 dark:border-dark-600"
+      >
+        <label class="input-label">{{ t('admin.accounts.modelRestriction') }}</label>
+
+        <div
+          v-if="isOpenAIModelRestrictionDisabled"
+          class="mb-3 rounded-lg bg-amber-50 p-3 dark:bg-amber-900/20"
+        >
+          <p class="text-xs text-amber-700 dark:text-amber-400">
+            {{ t('admin.accounts.openai.modelRestrictionDisabledByPassthrough') }}
+          </p>
+        </div>
+
+        <template v-else>
+          <!-- Mode Toggle -->
+          <div class="mb-4 flex gap-2">
+            <button
+              type="button"
+              @click="modelRestrictionMode = 'whitelist'"
+              :class="[
+                'flex-1 rounded-lg px-4 py-2 text-sm font-medium transition-all',
+                modelRestrictionMode === 'whitelist'
+                  ? 'bg-primary-100 text-primary-700 dark:bg-primary-900/30 dark:text-primary-400'
+                  : 'bg-gray-100 text-gray-600 hover:bg-gray-200 dark:bg-dark-600 dark:text-gray-400 dark:hover:bg-dark-500'
+              ]"
+            >
+              {{ t('admin.accounts.modelWhitelist') }}
+            </button>
+            <button
+              type="button"
+              @click="modelRestrictionMode = 'mapping'"
+              :class="[
+                'flex-1 rounded-lg px-4 py-2 text-sm font-medium transition-all',
+                modelRestrictionMode === 'mapping'
+                  ? 'bg-purple-100 text-purple-700 dark:bg-purple-900/30 dark:text-purple-400'
+                  : 'bg-gray-100 text-gray-600 hover:bg-gray-200 dark:bg-dark-600 dark:text-gray-400 dark:hover:bg-dark-500'
+              ]"
+            >
+              {{ t('admin.accounts.modelMapping') }}
+            </button>
+          </div>
+
+          <!-- Whitelist Mode -->
+          <div v-if="modelRestrictionMode === 'whitelist'">
+            <ModelWhitelistSelector v-model="allowedModels" :platform="form.platform" />
+            <p class="text-xs text-gray-500 dark:text-gray-400">
+              {{ t('admin.accounts.selectedModels', { count: allowedModels.length }) }}
+              <span v-if="allowedModels.length === 0">{{
+                t('admin.accounts.supportsAllModels')
+              }}</span>
+            </p>
+          </div>
+
+          <!-- Mapping Mode -->
+          <div v-else>
+            <div class="mb-3 rounded-lg bg-purple-50 p-3 dark:bg-purple-900/20">
+              <p class="text-xs text-purple-700 dark:text-purple-400">
+                {{ t('admin.accounts.mapRequestModels') }}
+              </p>
+            </div>
+
+            <div v-if="modelMappings.length > 0" class="mb-3 space-y-2">
+              <div
+                v-for="(mapping, index) in modelMappings"
+                :key="'oauth-' + getModelMappingKey(mapping)"
+                class="flex items-center gap-2"
+              >
+                <input
+                  v-model="mapping.from"
+                  type="text"
+                  class="input flex-1"
+                  :placeholder="t('admin.accounts.requestModel')"
+                />
+                <svg
+                  class="h-4 w-4 flex-shrink-0 text-gray-400"
+                  fill="none"
+                  viewBox="0 0 24 24"
+                  stroke="currentColor"
+                >
+                  <path
+                    stroke-linecap="round"
+                    stroke-linejoin="round"
+                    stroke-width="2"
+                    d="M14 5l7 7m0 0l-7 7m7-7H3"
+                  />
+                </svg>
+                <input
+                  v-model="mapping.to"
+                  type="text"
+                  class="input flex-1"
+                  :placeholder="t('admin.accounts.actualModel')"
+                />
+                <button
+                  type="button"
+                  @click="removeModelMapping(index)"
+                  class="rounded-lg p-2 text-red-500 transition-colors hover:bg-red-50 hover:text-red-600 dark:hover:bg-red-900/20"
+                >
+                  <svg class="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                    <path
+                      stroke-linecap="round"
+                      stroke-linejoin="round"
+                      stroke-width="2"
+                      d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
+                    />
+                  </svg>
+                </button>
+              </div>
+            </div>
+
+            <button
+              type="button"
+              @click="addModelMapping"
+              class="mb-3 w-full rounded-lg border-2 border-dashed border-gray-300 px-4 py-2 text-gray-600 transition-colors hover:border-gray-400 hover:text-gray-700 dark:border-dark-500 dark:text-gray-400 dark:hover:border-dark-400 dark:hover:text-gray-300"
+            >
+              + {{ t('admin.accounts.addMapping') }}
+            </button>
+
+            <!-- Quick Add Buttons -->
+            <div class="flex flex-wrap gap-2">
+              <button
+                v-for="preset in presetMappings"
+                :key="'oauth-' + preset.label"
+                type="button"
+                @click="addPresetMapping(preset.from, preset.to)"
+                :class="['rounded-lg px-3 py-1 text-xs transition-colors', preset.color]"
+              >
+                + {{ preset.label }}
+              </button>
+            </div>
+          </div>
+        </template>
+      </div>
+
       <!-- Temp Unschedulable Rules -->
       <div class="border-t border-gray-200 pt-4 dark:border-dark-600 space-y-4">
         <div class="mb-3 flex items-center justify-between">
@@ -3603,6 +3739,14 @@ const handleOpenAIExchange = async (authCode: string) => {
     const shouldCreateOpenAI = form.platform === 'openai'
     const shouldCreateSora = form.platform === 'sora'
 
+    // Add model mapping for OpenAI OAuth accounts（透传模式下不应用）
+    if (shouldCreateOpenAI && !isOpenAIModelRestrictionDisabled.value) {
+      const modelMapping = buildModelMappingObject(modelRestrictionMode.value, allowedModels.value, modelMappings.value)
+      if (modelMapping) {
+        credentials.model_mapping = modelMapping
+      }
+    }
+
     // 应用临时不可调度配置
     if (!applyTempUnschedConfig(credentials)) {
       return
@@ -3713,6 +3857,14 @@ const handleOpenAIValidateRT = async (refreshTokenInput: string) => {
         const oauthExtra = oauthClient.buildExtraInfo(tokenInfo) as Record<string, unknown> | undefined
         const extra = buildOpenAIExtra(oauthExtra)
 
+        // Add model mapping for OpenAI OAuth accounts（透传模式下不应用）
+        if (shouldCreateOpenAI && !isOpenAIModelRestrictionDisabled.value) {
+          const modelMapping = buildModelMappingObject(modelRestrictionMode.value, allowedModels.value, modelMappings.value)
+          if (modelMapping) {
+            credentials.model_mapping = modelMapping
+          }
+        }
+
         // Generate account name with index for batch
         const accountName = refreshTokens.length > 1 ? `${form.name} #${i + 1}` : form.name