fix: grant admin role to anonymous user and add DEFAULT_TOOL_VIEW env var

When AUTH_ENABLED=false, the anonymous user was assigned the "user" role
which lacks settings:write permission, making all settings saves return
403. Since no admin exists when auth is disabled, settings were
permanently read-only. Promote the anonymous user to "admin" so the
single user has full control of the instance.

Also adds DEFAULT_TOOL_VIEW env var (sidebar|fullscreen) following the
existing DEFAULT_THEME pattern, seeded via ensureDefaultSettings() on
first boot.

Closes #135

apps/api/src/plugins/auth.ts

@@ -847,13 +847,11 @@ function isPublicRoute(url: string): boolean {
 
 export async function authMiddleware(app: FastifyInstance): Promise<void> {
   app.addHook("preHandler", async (request: FastifyRequest, reply: FastifyReply) => {
-    // When auth is disabled, attach a synthetic non-admin user so tools work
-    // but admin-only routes (user management, settings write, etc.) stay locked
     if (!env.AUTH_ENABLED) {
       (request as FastifyRequest & { user?: AuthUser }).user = {
         id: "anonymous",
         username: "anonymous",
-        role: "user",
+        role: "admin",
       };
       return;
     }