Add history-ui workspace and supporting server endpoints

Splits history-ui out of asch/fix-everything into its own branch off
main. Includes the Svelte workspace, the three dedicated server
endpoints (list_vaults, fetch_vault_history, fetch_document_versions),
SPA asset embedding via rust-embed, and the matching TS mirror types in
sync-client.

Note: this branch will not compile against main on its own — the new
endpoints depend on database/error/config additions that live on
asch/fix-everything. Intended to be merged once asch/fix-everything
lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/history-ui/package.json

@@ -0,0 +1,16 @@
+{
+    "name": "history-ui",
+    "version": "0.14.0",
+    "private": true,
+    "type": "module",
+    "scripts": {
+        "dev": "vite dev --host 0.0.0.0",
+        "build": "vite build",
+        "test": "echo 'no tests yet'"
+    },
+    "devDependencies": {
+        "@sveltejs/vite-plugin-svelte": "^5.0.0",
+        "svelte": "^5.0.0",
+        "vite": "^6.0.0"
+    }
+}