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/vite.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from "vite";
+import { svelte } from "@sveltejs/vite-plugin-svelte";
+
+export default defineConfig({
+    plugins: [svelte()],
+    build: {
+        outDir: "dist",
+        emptyOutDir: true
+    },
+    server: {
+        proxy: {
+            "/vaults": "http://localhost:3010"
+        }
+    }
+});