feat: add candlestick chart with portfolio value line (BT-004)

- Add spot_open field to BacktestDailyPoint for complete OHLC data
- Replace line chart with candlestick chart showing price OHLC
- Add portfolio value line on secondary Y-axis
- Add _chart_options_from_dict for rendering job results
- Update both render_result and render_job_result to use new chart

docs/roadmap/ROADMAP.yaml

@@ -13,7 +13,6 @@ notes:
   - Pre-alpha policy: we may cut or replace old features without backward compatibility until alpha is declared.
   - Alpha migration policy: once alpha is declared, compatibility only needs to move forward; backward migrations are not required.
 priority_queue:
-  - BT-004
   - EXEC-002
   - DATA-DB-005
   - DATA-002A
@@ -24,6 +23,7 @@ priority_queue:
   - GCF-001
   - DATA-DB-006
 recently_completed:
+  - BT-004
   - BT-005
   - CORE-003
   - CONV-001
@@ -50,7 +50,6 @@ recently_completed:
   - CORE-002B
 states:
   backlog:
-    - BT-004
     - DATA-DB-005
     - DATA-DB-006
     - EXEC-002
@@ -62,6 +61,7 @@ states:
     - GCF-001
   in_progress: []
   done:
+    - BT-004
     - BT-005
     - CORE-003
     - CONV-001

docs/roadmap/done/BT-004-backtest-visualization-chart.yaml

@@ -1,6 +1,6 @@
 id: BT-004
 title: Backtest Visualization Chart
-status: backlog
+status: done
 priority: P1
 effort: M
 depends_on:
@@ -14,6 +14,6 @@ acceptance_criteria:
   - Chart is responsive and readable on mobile/tablet viewports.
   - Chart library matches existing app styling (dark mode support).
 notes: |
-  Consider using a lightweight charting library that integrates well with NiceGUI.
-  Portfolio value line should be clearly distinguishable from candlesticks.
-  May want to add toggle for showing/hiding different series.
+  Implemented using ECharts candlestick series with portfolio value line on secondary Y-axis.
+  Added spot_open field to BacktestDailyPoint for complete OHLC data.
+  Charts render for both immediate results and async job results.