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/sync-client/src/services/types/ListVaultsResponse.ts

@@ -0,0 +1,11 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+import type { VaultInfo } from "./VaultInfo";
+
+/**
+ * Response to listing vaults accessible to the authenticated user.
+ */
+export interface ListVaultsResponse {
+    vaults: VaultInfo[];
+    hasMore: boolean;
+    userName: string;
+}

frontend/sync-client/src/services/types/VaultHistoryResponse.ts

@@ -0,0 +1,10 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+import type { DocumentVersionWithoutContent } from "./DocumentVersionWithoutContent";
+
+/**
+ * Response to a vault history request (paginated).
+ */
+export interface VaultHistoryResponse {
+    versions: DocumentVersionWithoutContent[];
+    hasMore: boolean;
+}

frontend/sync-client/src/services/types/VaultInfo.ts

@@ -0,0 +1,10 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+/**
+ * Summary of a single vault returned by the list-vaults endpoint.
+ */
+export interface VaultInfo {
+    name: string;
+    documentCount: number;
+    createdAt: string | null;
+}