Fix Me tab Gravatar icon not updating on first launch

[thirumani-vihaan]

Description

Fixes: #21415

On the very first launch (after a fresh app install and login), the Gravatar icon in the bottom navigation "Me" tab does not appear immediately. It requires a hard restart of the app to become visible.

This happens because the account record syncs asynchronously. By the time WPMainNavigationView is initialized, the avatarUrl might not be available yet. An onAccountChanged event fires in WPMainActivity once the user's account data successfully loads, but the bottom navigation view was never instructed to refresh its Gravatar icon dynamically.

Changes made:

1. Added a refreshGravatar() method to WPMainNavigationView.kt that fetches the "Me" tab ImageView and safely updates it via loadGravatar() using the latest accountStore.account?.avatarUrl.
2. Updated WPMainActivity.java inside onAccountChanged to invoke mBottomNav.refreshGravatar() when an updated account event is broadcasted.

Testing instructions

Fresh Install First-Run Avatar Load:

1. Install a fresh build of the app (or clear all app data).
2. Log into an account that has a Gravatar image set.

• Verify that as soon as the login completes and you reach the main screen, the Gravatar image successfully appears on the "Me" tab (bottom right) without requiring an app restart.

3. Log out and log back in with a different account.

• Verify the new account's Gravatar immediately loads on the "Me" tab.