feat(rectifier): 请求整流器增加 API Key 账号签名整流支持

新增独立开关控制 API Key 账号的签名整流功能，支持配置自定义
匹配关键词以捕获不同格式的上游错误响应。

- 新增 apikey_signature_enabled 开关（默认关闭）
- 新增 apikey_signature_patterns 自定义关键词配置
- 内置签名检测规则对 API Key 账号同样生效
- 自定义关键词对完整响应体做不区分大小写匹配
- 重试二阶段检测仅做模式匹配，不重复校验开关
- Handler 层校验关键词数量（≤50）和长度（≤500）
- API 响应 nil patterns 统一序列化为空数组
- OAuth/SetupToken/Upstream/Bedrock 账号行为不变

frontend/src/views/admin/SettingsView.vue

@@ -454,6 +454,72 @@
                   </div>
                   <Toggle v-model="rectifierForm.thinking_budget_enabled" />
                 </div>
+
+                <!-- API Key Signature Rectifier -->
+                <div class="flex items-center justify-between">
+                  <div>
+                    <label class="text-sm font-medium text-gray-700 dark:text-gray-300">{{
+                      t('admin.settings.rectifier.apikeySignature')
+                    }}</label>
+                    <p class="text-xs text-gray-500 dark:text-gray-400">
+                      {{ t('admin.settings.rectifier.apikeySignatureHint') }}
+                    </p>
+                  </div>
+                  <Toggle v-model="rectifierForm.apikey_signature_enabled" />
+                </div>
+
+                <!-- Custom Patterns (only when apikey_signature_enabled) -->
+                <div
+                  v-if="rectifierForm.apikey_signature_enabled"
+                  class="ml-4 space-y-3 border-l-2 border-gray-200 pl-4 dark:border-dark-600"
+                >
+                  <div>
+                    <label class="text-sm font-medium text-gray-700 dark:text-gray-300">{{
+                      t('admin.settings.rectifier.apikeyPatterns')
+                    }}</label>
+                    <p class="text-xs text-gray-500 dark:text-gray-400">
+                      {{ t('admin.settings.rectifier.apikeyPatternsHint') }}
+                    </p>
+                  </div>
+                  <div
+                    v-for="(_, index) in rectifierForm.apikey_signature_patterns"
+                    :key="index"
+                    class="flex items-center gap-2"
+                  >
+                    <input
+                      v-model="rectifierForm.apikey_signature_patterns[index]"
+                      type="text"
+                      class="input input-sm flex-1"
+                      :placeholder="t('admin.settings.rectifier.apikeyPatternPlaceholder')"
+                    />
+                    <button
+                      type="button"
+                      @click="rectifierForm.apikey_signature_patterns.splice(index, 1)"
+                      class="btn btn-ghost btn-xs text-red-500 hover:text-red-700"
+                    >
+                      <svg
+                        class="h-4 w-4"
+                        fill="none"
+                        stroke="currentColor"
+                        viewBox="0 0 24 24"
+                      >
+                        <path
+                          stroke-linecap="round"
+                          stroke-linejoin="round"
+                          stroke-width="2"
+                          d="M6 18L18 6M6 6l12 12"
+                        />
+                      </svg>
+                    </button>
+                  </div>
+                  <button
+                    type="button"
+                    @click="rectifierForm.apikey_signature_patterns.push('')"
+                    class="btn btn-ghost btn-xs text-primary-600 dark:text-primary-400"
+                  >
+                    + {{ t('admin.settings.rectifier.addPattern') }}
+                  </button>
+                </div>
               </div>
 
               <!-- Save Button -->
@@ -2010,7 +2076,9 @@ const rectifierSaving = ref(false)
 const rectifierForm = reactive({
   enabled: true,
   thinking_signature_enabled: true,
-  thinking_budget_enabled: true
+  thinking_budget_enabled: true,
+  apikey_signature_enabled: false,
+  apikey_signature_patterns: [] as string[]
 })
 
 // Beta Policy 状态
@@ -2626,6 +2694,10 @@ async function loadRectifierSettings() {
   try {
     const settings = await adminAPI.settings.getRectifierSettings()
     Object.assign(rectifierForm, settings)
+    // 确保 patterns 是数组（旧数据可能为 null）
+    if (!Array.isArray(rectifierForm.apikey_signature_patterns)) {
+      rectifierForm.apikey_signature_patterns = []
+    }
   } catch (error: any) {
     console.error('Failed to load rectifier settings:', error)
   } finally {
@@ -2639,9 +2711,16 @@ async function saveRectifierSettings() {
     const updated = await adminAPI.settings.updateRectifierSettings({
       enabled: rectifierForm.enabled,
       thinking_signature_enabled: rectifierForm.thinking_signature_enabled,
-      thinking_budget_enabled: rectifierForm.thinking_budget_enabled
+      thinking_budget_enabled: rectifierForm.thinking_budget_enabled,
+      apikey_signature_enabled: rectifierForm.apikey_signature_enabled,
+      apikey_signature_patterns: rectifierForm.apikey_signature_patterns.filter(
+        (p) => p.trim() !== ''
+      )
     })
     Object.assign(rectifierForm, updated)
+    if (!Array.isArray(rectifierForm.apikey_signature_patterns)) {
+      rectifierForm.apikey_signature_patterns = []
+    }
     appStore.showSuccess(t('admin.settings.rectifier.saved'))
   } catch (error: any) {
     appStore.showError(