add mock settings page

src/routes/settings/+layout.svelte

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+
+<script lang="ts">
+    import MenuLink from "$lib/MenuLink.svelte";
+    import SLayout from "$lib/SLayout.svelte";
+    import { RiBrush2Line } from "svelte-remixicon";
+
+let { children } = $props();
+</script>
+
+
+<SLayout title="Settings">
+    {@render children()}
+    {#snippet left()}
+        <ul class="column">
+            <MenuLink href="/settings/appearance" icon={RiBrush2Line} label="Appearance" />
+        </ul>
+    {/snippet}
+    {#snippet right()}
+        <button class="primary card">Save</button>
+    {/snippet}
+</SLayout>

src/routes/settings/+page.svelte

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+
+Select a setting from the left menu to change its settings

src/routes/settings/appearance/+page.svelte

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+
+TODO