[FIX] portal: raise front-end asset priority

This is necessary to make it among the first of the "assets frontend"
inherited views, and specifically make it appear *before* the one from
website. Without this, SCSS styles may be randomly broken if the
original installation order of `portal` and `website` was reversed
(e.g. for older databases).

addons/portal/views/assets.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <odoo>
-    <template id="assets_frontend" inherit_id="web.assets_frontend" name="Portal Assets">
+    <template id="assets_frontend" inherit_id="web.assets_frontend" name="Portal Assets" priority="15">
         <xpath expr="//link[last()]" position="after">
             <link rel="stylesheet" type="text/scss" href="/portal/static/src/scss/bootstrap.extend.scss"/>
             <link rel="stylesheet" type="text/scss" href="/portal/static/src/scss/portal.scss"/>