feat(phase3): phase 7 - integration & polish

Fix all build/type/lint errors, write 46 new tests (222 total across
20 files), regenerate Prisma client, update seed with user preferences.
Fix SvelteSet usage, add {#each} keys, clean unused imports.

src/lib/components/widget/AppWidget.svelte

@@ -1,5 +1,4 @@
 <script lang="ts">
-	import { t } from 'svelte-i18n';
 	import { onMount } from 'svelte';
 	import AppHealthBadge from '$lib/components/app/AppHealthBadge.svelte';
 	import SparklineChart from '$lib/components/app/SparklineChart.svelte';