iOS 26: Fix visual issues in the Site Creation flow

[kean]

Before

Simulator.Screen.Recording.-.iPhone.17.-.2025-09-19.at.08.04.35.mov

After (iOS 26)

Note: the search bar shadow is still not ideal, but I ran out of time today. I need to switch to the other projects. It fixes the main issues.

After (iOS 18)

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	29086
	Version	PR #24865
	Bundle ID	com.jetpack.alpha
	Commit	8b6da98
	Installation URL	1d2m4ofisig5o

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	29086
	Version	PR #24865
	Bundle ID	org.wordpress.alpha
	Commit	8b6da98
	Installation URL	24r6bjf7pg0gg

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.