UI: full-stack test coverage with tabs for Query, Storage, AI, Status

- Query tab: SQL editor with results table (existing)
- Storage tab: list objects, register datasets pointing at storage keys
- AI tab: embed (nomic-embed-text), generate (qwen2.5), rerank with scored results
- Status tab: health checks for all 5 services + functional tests (embed, generate, SQL)
- nginx: added /lakehouse/ and API proxy paths to devop.live config
- Loaded 3 sample datasets: employees, events, products
- Fixed Rust 2024 reserved keyword `gen`

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

data/_catalog/manifests/1f81445a-404f-48ea-bd72-00f6721ee18b.json

@@ -0,0 +1,15 @@
+{
+  "id": "1f81445a-404f-48ea-bd72-00f6721ee18b",
+  "name": "employees",
+  "schema_fingerprint": "auto",
+  "objects": [
+    {
+      "bucket": "data",
+      "key": "datasets/employees.parquet",
+      "size_bytes": 1424,
+      "created_at": "2026-03-27T11:55:55.013996293Z"
+    }
+  ],
+  "created_at": "2026-03-27T11:55:55.014010258Z",
+  "updated_at": "2026-03-27T11:55:55.014010258Z"
+}