docs: mark DATA-DB-004 as done, update roadmap

docs/roadmap/done/DATA-DB-004-backtest-page-ui-updates.yaml

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+id: DATA-DB-004
+title: Backtest Page UI Updates
+status: backlog
+priority: high
+dependencies:
+  - DATA-DB-001
+  - DATA-DB-002
+estimated_effort: 2 days
+created: 2026-03-28
+updated: 2026-03-28
+
+description: |
+  Update backtest and event comparison pages to support Databento data source
+  and independent scenario configuration. Show estimated data cost and cache
+  status in the UI.
+
+acceptance_criteria:
+  - Data source selector shows Databento and yFinance options
+  - Databento config shows dataset and resolution dropdowns
+  - Dataset selection updates cost estimate display
+  - Cache status shows age of cached data
+  - Independent start price input (0 = auto-derive)
+  - Independent underlying units and loan amount
+  - Event comparison page uses same data source config
+  - Settings persist across sessions
+
+implementation_notes: |
+  Page changes:
+  
+  Backtests page:
+  - Add "Data Source" section with Databento/yFinance toggle
+  - Add dataset selector (XNAS.BASIC for GLD, GLBX.MDP3 for GC=F)
+  - Add resolution selector (ohlcv-1d, ohlcv-1h)
+  - Show estimated cost with refresh button
+  - Show cache status (age, size)
+  - "Configure Scenario" section with independent start price/units
+  
+  Event comparison page:
+  - Same data source configuration
+  - Preset scenarios show if data cached
+  - Cost estimate for missing data
+  
+  State management:
+  - Use workspace-level BacktestSettings
+  - Load on page mount, save on change
+  - Invalidate cache when params change
+
+dependencies_detail:
+  - DATA-DB-001: Need DatabentoHistoricalPriceSource
+  - DATA-DB-002: Need BacktestSettings model