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/ui/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "ui"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+dioxus = { version = "0.7", features = ["web"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tracing = "0.1"
+reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
+web-sys = { version = "0.3", features = ["Window", "Location"] }