feat(mediaserver): 飞牛影视增加访问码配置项

配置弹窗与初始化向导的飞牛表单增加访问码输入项，未开启时留空。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/components/dialog/MediaServerInfoDialog.vue

@@ -454,6 +454,17 @@ onMounted(() => {
                   prepend-inner-icon="mdi-lock"
                 />
               </VCol>
+              <VCol cols="12" md="6">
+                <VTextField
+                  type="password"
+                  v-model="mediaServerInfo.config.access_code"
+                  :label="t('mediaserver.accessCode')"
+                  :hint="t('mediaserver.accessCodeHint')"
+                  persistent-hint
+                  active
+                  prepend-inner-icon="mdi-shield-key"
+                />
+              </VCol>
               <VCol cols="12" md="6">
                 <VTextField
                   v-model.number="mediaServerInfo.sync_interval"