fix: Refine verify email dialog for verify and change email flows (#14671)

### Summary
This PR improves the verify email dialog by giving the verify-email and
change-email flows distinct messaging instead of reusing the same
generic copy.

### What changed
* Use flow-specific body copy in the verify email dialog
* Keep the existing action-specific subtitle behavior for:
  * Verify email
  * Change email
* Update the English i18n strings so each flow explains the correct
intent:
  * Verify email focuses on confirming email ownership
  * Change email focuses on securely starting the email-change process
### Why
The previous dialog message was shared across both flows, which made the
change-email experience feel ambiguous. This update makes the intent
clearer for users and better matches the action they are taking.



https://www.loom.com/share/c64c20570a8242358bd178a2ac50e413


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved clarity in email verification and email change dialog
messages to better explain the confirmation process and link purpose.
* Enhanced distinction between email verification and email change
workflows with context-specific messaging.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/desktop/dialogs/verify-email/index.tsx

@@ -108,10 +108,18 @@ export const VerifyEmailDialog = ({
     >
       <AuthHeader
         title={serverName}
-        subTitle={t['com.affine.settings.email.action.change']()}
+        subTitle={
+          changeEmail
+            ? t['com.affine.settings.email.action.change']()
+            : t['com.affine.settings.email.action.verify']()
+        }
       />
       <AuthContent>
-        <p>{t['com.affine.auth.verify.email.message']({ email })}</p>
+        <p>
+          {changeEmail
+            ? t['com.affine.auth.change.email.message']({ email })
+            : t['com.affine.auth.verify.email.message']({ email })}
+        </p>
         <AuthInput
           label={t['com.affine.settings.email']()}
           disabled={true}