feat(ui,infra): SvelteKit ui scaffold, Makefile, pre-commit, claude hooks

ui/: SvelteKit 2 + Svelte 5 + Tailwind 4 + shadcn-svelte (luma, lucide)
on bun with ultracite; adapter-static with SPA fallback; theme tokens
taken from msos. Dockerfile gains a bun stage that builds ui/build.
Makefile and pre-commit cover ruff, ty, ultracite and svelte-check;
.claude settings run the matching fixer after edits. docs/PRODUCT.md
captures product truth for the UI work.

ui/src/routes/+layout.svelte

@@ -0,0 +1,9 @@
+<script lang="ts">
+  import "./layout.css";
+  import favicon from "$lib/assets/favicon.svg";
+
+  let { children } = $props();
+</script>
+
+<svelte:head><link href={favicon} rel="icon"></svelte:head>
+{@render children()}