split: history-ui (new Svelte workspace)

New web UI for browsing vault history. Svelte + Vite app with components
for activity feed, dashboard, document detail, diff view, file tree,
header, login, time slider, toast container, vault picker; lib/api.ts and
stores.svelte.ts for client state. (Generated TS types were added in
PR6.)

frontend/history-ui/svelte.config.js

@@ -0,0 +1,5 @@
+import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";
+
+export default {
+    preprocess: vitePreprocess()
+};