fix(strategy): calculate total PnL percentage correctly in portfolio summary (#489)

## 📝 Pull Request Template

### 1. Related Issue
Closes # (issue number)

### 2. Type of Change (select one)
Type of Change: Bug Fix / New Feature / Code Refactor / Documentation
Update / Other: __________

### 3. Description
Please describe the changes made and why they are necessary.

### 4. Testing
- [ ] I have tested this locally.
- [ ] I have updated or added relevant tests.

### 5. Checklist
- [ ] I have read the [Code of Conduct](./CODE_OF_CONDUCT.md)
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- [ ] My changes follow the project's coding style

Author: vcfgv

python/valuecell/server/services/strategy_service.py

@@ -130,7 +130,7 @@ async def get_strategy_portfolio_summary(
             cash=_to_optional_float(snapshot.cash),
             total_value=total_value,
             total_pnl=total_pnl,
-            total_pnl_pct=total_pnl_pct,
+            total_pnl_pct=_to_optional_float(total_pnl_pct) * 100.0,
             gross_exposure=_to_optional_float(
                 getattr(snapshot, "gross_exposure", None)
             ),