feat: Data Explorer tab + manual data entry with live CDC

Add a dedicated business-data view (separate from infra/search):
- New "Data Explorer" tab: KPIs (customers, employees, products, source
  row totals, sample revenue) + charts driven by Elasticsearch aggregations
  (revenue over time, by region/channel/status, top customers & products,
  HR by department/role/event, supply chain by type, telemetry averages),
  with region + free-text filters.
- Backend /api/search/business endpoint: battery of ES aggregations with
  numeric/date index template (so amount sums and date histograms work),
  source totals via cheap planner estimates; biased the orders sample to
  rows carrying customer names so people are searchable/visible.

Manual data entry on source systems:
- "Insert row" action in the Data Hub browser opens a column-aware form;
  POST /api/sql/row/insert writes to Postgres/MySQL/Mongo/Cassandra/Neo4j.
- Inserts into CDC sources (PG/MySQL/Mongo) are captured by Debezium and
  streamed to Kafka in real time; UI flags this and pulses the data flow.

ui/src/App.tsx

@@ -18,6 +18,7 @@ import { StorageView } from './components/features/StorageView'
 import { ChangesView } from './components/features/ChangesView'
 import { DataFlowView } from './components/features/DataFlowView'
 import { SearchView } from './components/features/SearchView'
+import { DataExplorerView } from './components/features/DataExplorerView'
 import { DataHubView } from './components/features/DataHubView'
 import { SshTerminal } from './components/features/SshTerminal'
 import { TerminalDock } from './components/features/TerminalDock'
@@ -141,6 +142,8 @@ export default function App() {
                   <StorageView />
                 ) : cc.mainView === 'search' ? (
                   <SearchView />
+                ) : cc.mainView === 'dataexplorer' ? (
+                  <DataExplorerView />
                 ) : (
                   <ApprovalInbox agents={cc.agents} livePending={cc.approvals} onDecide={cc.decide} />
                 )}