chore: Adjust default Anvil/WDS border radius (#40088)

## Description

Fixes #39900  

| Before | After |
|--------|--------|
| <img width="746" alt="Screenshot 2025-04-04 at 12 28 54"
src="https://github.com/user-attachments/assets/8e36f87d-8340-4b83-92d4-9e3ff2525f4d"
/> | <img width="707" alt="Screenshot 2025-04-04 at 12 41 51"
src="https://github.com/user-attachments/assets/e786f8e8-0a7e-4a9c-8671-536962622ea2"
/> |

## Automation

/ok-to-test tags="@tag.Sanity"

### 🔍 Cypress test results
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> [!CAUTION]  
> If you modify the content in this section, you are likely to disrupt
the CI result for your PR.

<!-- end of auto-generated comment: Cypress test results  -->


## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [x] No

app/client/packages/design-system/theming/src/token/src/defaultTokens.json

@@ -2,7 +2,7 @@
   "seedColor": "#0080ff",
   "colorMode": "light",
   "borderRadiusElevation": {
-    "base": "0px",
+    "base": "8px",
     "1": "calc(var(--border-radius-elevation-base) + var(--outer-spacing-1) * 2)",
     "2": "calc(var(--border-radius-elevation-base) + var(--outer-spacing-1))",
     "3": "var(--border-radius-elevation-base)"

app/client/packages/storybook/src/components/ThemeSettings.tsx

@@ -98,8 +98,8 @@ export const ThemeSettings = ({
               size="100%"
               title="Border Radius"
             >
+              <option value="8px">Rounded</option>
               <option value="0px">Sharp</option>
-              <option value="6px">Rounded</option>
               <option value="20px">Pill</option>
             </StyledSelect>
           </Flex>

app/client/src/constants/AppConstants.ts

@@ -131,7 +131,7 @@ export const defaultThemeSetting: ThemeSetting = {
   fontFamily: "System Default",
   accentColor: "#0080ff",
   colorMode: "LIGHT",
-  borderRadius: "6px",
+  borderRadius: "8px",
   density: 1,
   sizing: 1,
   appMaxWidth: APP_MAX_WIDTH.Large,

app/client/src/pages/Editor/WDSThemePropertyPane/constants.ts

@@ -41,7 +41,7 @@ export const THEME_SETTINGS_SIZING_OPTIONS = [
 
 export const THEME_SETTINGS_BORDER_RADIUS_OPTIONS = [
   { label: "Sharp", value: "0px" },
-  { label: "Rounded", value: "6px" },
+  { label: "Rounded", value: "8px" },
   { label: "Pill", value: "20px" },
 ];