chore: fix WalletScreen navbar onPress while scrolled

[benisgold]

Fixes APP-2134

What changed (plus any additional context for devs)

Problem

A change in PR #5496 made the wallet name button in the WalletScreen navbar non-interactive. While attempting to ensure the QR and settings buttons remained pressable by adding a negative zIndex to the wallet name component, the wallet name button was inadvertently placed behind the navbar, making it inaccessible.

Solution

• Removed the negative zIndex from the wallet name component
• Adjusted its incorrectly calculated maxWidth constraint to prevent the wallet name from overlapping with QR and settings buttons

Screen recordings / screenshots

Simulator.Screen.Recording.-.iPhone.16.Pro.-.2024-12-07.at.16.58.31.mp4

What to test

• long wallet names are properly displayed/truncated
• long wallet names do not interfere with other navbar buttons
• pressing wallet name on navbar opens the ChangeWalletSheet regardless of whether screen is scrolled

[linear]

APP-2134 Wallet Screen sticky header onPress doesn't work while scrolled

[brunobar79]

Launch in simulator or device for e37e1ed

[maxbbb]

lgtm. e2e fail looks unrelated.