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>

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@@ -0,0 +1,15 @@
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data/_catalog/manifests/f4c0f89b-85bf-4af6-8692-8e1cc81c357a.json

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+  "name": "scores",
+  "schema_fingerprint": "test",
+  "objects": [
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+}