Phase 4: Dioxus frontend with dataset browser and SQL query editor

- ui: Dioxus WASM app with dataset sidebar, SQL editor (Ctrl+Enter), results table
- ui: dynamic API base URL (same-origin for nginx, port-based for local dev)
- gateway: CORS enabled for cross-origin requests
- nginx: lakehouse.devop.live proxies UI (:3300) + API (:3100) on same origin
- justfile: ui-build, ui-serve, sidecar, up commands added

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/gateway/src/main.rs

@@ -1,4 +1,5 @@
 use axum::{Router, routing::get};
+use tower_http::cors::{Any, CorsLayer};
 use tower_http::trace::TraceLayer;
 use tracing_subscriber::{EnvFilter, fmt, layer::SubscriberExt, util::SubscriberInitExt};
 
@@ -32,6 +33,10 @@ async fn main() {
         .nest("/catalog", catalogd::service::router(registry))
         .nest("/query", queryd::service::router(engine))
         .nest("/ai", aibridge::service::router(ai_client))
+        .layer(CorsLayer::new()
+            .allow_origin(Any)
+            .allow_methods(Any)
+            .allow_headers(Any))
         .layer(TraceLayer::new_for_http());
 
     let addr = "0.0.0.0:3100";