drop multi-node ssh execution, unify job runner to local + fix job completion atomicity

- remove nodes table, ssh service, nodes api, NodesPage route
- execute.ts: local-only spawn, atomic CAS job claim via UPDATE status
- wrap job done + subtitle_files insert + review_plans status in db transaction
- stream ffmpeg output per line with 500ms throttled flush
- bump version to 2026.04.13

src/routes/__root.tsx

@@ -56,7 +56,6 @@ function RootLayout() {
 				</div>
 				<div className="flex-1" />
 				<div className="flex items-center gap-0.5">
-					<NavLink to="/nodes">Nodes</NavLink>
 					<NavLink to="/settings">Settings</NavLink>
 				</div>
 			</nav>