chore: état initial avant refonte (atlas SvelteKit v4.0.0)

Snapshot de l'existant avant application du playbook OKI :
background shader Three.js, carte graphe 3D, timeline statique.

atlas-fediverse/src/lib/components/pages/FeatureGrid.svelte

@@ -0,0 +1,80 @@
+<script lang="ts">
+	import Icon, { type IconName } from './Icon.svelte';
+
+	export interface FeatureItem {
+		icon: IconName;
+		title: string;
+		description: string;
+	}
+
+	interface Props {
+		items: FeatureItem[];
+		/** Taille minimale des colonnes de la grille (primitive .grid). */
+		min?: string;
+	}
+
+	let { items, min = '15rem' }: Props = $props();
+</script>
+
+<div class="feature-cq">
+	<ul class="grid" role="list" style:--grid-min={min}>
+		{#each items as item (item.title)}
+			<li class="feature-card">
+				<span class="feature-icon"><Icon name={item.icon} /></span>
+				<div class="feature-text">
+					<h3>{item.title}</h3>
+					<p>{item.description}</p>
+				</div>
+			</li>
+		{/each}
+	</ul>
+</div>
+
+<style>
+	/* Container query : la carte passe en disposition horizontale
+	   quand son conteneur (pas le viewport) est assez large. */
+	.feature-cq {
+		container-type: inline-size;
+	}
+
+	.feature-card {
+		display: flex;
+		flex-direction: column;
+		align-items: flex-start;
+		gap: var(--space-3);
+		padding: var(--space-4);
+		background: var(--glass);
+		backdrop-filter: blur(12px);
+		-webkit-backdrop-filter: blur(12px);
+		border: 1px solid var(--glass-border);
+		border-radius: var(--radius-2);
+	}
+
+	.feature-icon {
+		display: inline-flex;
+		align-items: center;
+		justify-content: center;
+		inline-size: 2.75rem;
+		block-size: 2.75rem;
+		flex-shrink: 0;
+		border-radius: var(--radius-1);
+		color: var(--page-accent-text, var(--accent-text));
+		background: color-mix(in oklch, var(--page-accent, var(--accent)) 14%, transparent);
+	}
+
+	h3 {
+		font-size: var(--text-1);
+		margin-block-end: var(--space-1);
+	}
+
+	p {
+		font-size: var(--text-small);
+		color: var(--ink-soft);
+	}
+
+	@container (min-width: 30rem) {
+		.feature-card {
+			flex-direction: row;
+		}
+	}
+</style>