chore: add commas to PnL (MetaMask#27815)

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## **Description**
 Add commas to PnL

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CHANGELOG entry: add commas to PnL

## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/ASSETS-2966

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk UI-only change to how the price difference (PnL) value is
formatted and signed in `AssetOverview`.
> 
> **Overview**
> Improves the `AssetOverview` price-diff (PnL) label formatting by
switching from `addCurrencySymbol(diff, ...)` to
`formatPriceWithSubscriptNotation(Math.abs(diff), ...)`, which adds
thousands separators and consistent small-value formatting.
> 
> Also fixes sign rendering so negative diffs show a leading `-`
(positive keeps `+`, zero shows no sign) while keeping the percentage
calculation display unchanged.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
4055c10. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: juanmigdr

app/components/UI/AssetOverview/Price/Price.tsx

@@ -129,8 +129,14 @@ const Price = ({
               variant={TextVariant.BodyMDMedium}
               allowFontScaling={false}
             >
-              {diff > 0 ? '+' : ''}
-              {addCurrencySymbol(diff, currentCurrency, true)} (
+              {diff > 0 ? '+' : diff < 0 ? '-' : ''}
+              {diff !== 0
+                ? formatPriceWithSubscriptNotation(
+                    Math.abs(diff),
+                    currentCurrency,
+                  )
+                : addCurrencySymbol(0, currentCurrency, true)}{' '}
+              {'('}
               {diff > 0 ? '+' : ''}
               {diff === 0 ? '0' : ((diff / comparePrice) * 100).toFixed(2)}
               %){' '}