nixos/services: lay ground for gitea branding

also makes adds gitea persistence

assets/gitea/templates/home.tmpl

@@ -0,0 +1,12 @@
+{{template "base/head" .}}
+<div role="main" aria-label="{{if .IsSigned}}{{ctx.Locale.Tr "dashboard"}}{{else}}{{ctx.Locale.Tr "home"}}{{end}}"
+   class="page-content home tw-mb-8 tw-px-8 center" style="height: 100%; flex-direction: column; display: flex; align-items: center; justify-content: space-around;">
+   <img width="500" height="500" src="{{AssetUrlPrefix}}/images/full-logo.svg" alt="{{ctx.Locale.Tr "logo"}}">
+   <div class="hero">
+      <h1 class="ui icon header title">
+         {{AppName}}
+      </h1>
+      <!-- <h2>My own gitea server 😎</h2> -->
+   </div>
+</div>
+{{template "base/footer" .}}