feat: 页脚优先展示后台配置的页脚 Logo

- CmsSiteInfo 加 websiteFooterLogo 类型
- useSite 新增 siteFooterLogo(websiteFooterLogo 优先，回退
  siteLogo)；siteLogo/siteFooterLogo 统一过 ensureFullUrl，
  兼容本地存储相对路径(/api/file 代理)与完整 OSS URL
- template-01~08/10 共 9 个模板 Footer 的 SiteBrand 改用
  siteFooterLogo；template-09 页脚无品牌区保持不变
- 未配置页脚 Logo 时行为与旧版完全一致(回退站点 Logo)

app/templates/template-03/components/Footer.vue

@@ -6,7 +6,7 @@
         <div class="max-w-xs">
           <SiteBrand
             link-class="mb-2"
-            :logo="siteLogo"
+            :logo="siteFooterLogo"
             :icon="siteIcon"
             :name="siteName"
             logo-class="h-8 w-auto max-w-[180px] object-contain"
@@ -80,7 +80,7 @@
  */
 import type { CmsNavigation } from '~/types'
 
-const { siteInfo, siteName, siteLogo, siteIcon, siteConfig, bottomNavigations, phone, email, address, copyright, wxQrcode, icpNo, slogan, officialWebsite, officialWebsiteUrl, socialLinks } = useSite()
+const { siteInfo, siteName, siteLogo, siteFooterLogo, siteIcon, siteConfig, bottomNavigations, phone, email, address, copyright, wxQrcode, icpNo, slogan, officialWebsite, officialWebsiteUrl, socialLinks } = useSite()
 
 /** 快速链接：取顶级导航中非首页且无子菜单的项 */
 const quickLinks = computed<CmsNavigation[]>(() => {