iOS 26: Minor visual fixes

[kean]

See the individual commit message for changes: slightly larger spacing, fixing unwanted back button titles, integrating native "done" buttons, etc.

Screenshots

An issue with an empty space in the notifications:

New native done buttons in "Post Settings" (grayed out inactive on screenshot)

Slightly more breezing room on dashboard.

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
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	29214
	Version	PR #24890
	Bundle ID	com.jetpack.alpha
	Commit	cab6a49
	Installation URL	4ctag39qg7vt0

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	29214
	Version	PR #24890
	Bundle ID	org.wordpress.alpha
	Commit	cab6a49
	Installation URL	1a1g6auec2au0

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

[sentry]

Issues attributed to commits in this pull request

This pull request was merged and Sentry observed the following issues:

• ‼️ Error Domain=WPAssertionFailure Code=-1 "PostSetti... in alpha