[url_launcher] Modernize url_launcher_ios example

[stuartmorgan-g]

Replaces the Obj-C example app with Swift. Rather than attempt to modify the example in place, I started clean from the Swift template:

• deleted the ios/ directory.
• ran flutter create --platforms=ios . using current stable (3.41.0).
• re-did the RunnerUITest setup process, and swapped in the existing test files for that and RunnerTest.
• ran native tests and the example app to capture the auto-migration steps for CocoaPods.

In addition, I did some cleanup on the Dart part of this example, which had never been updated post-federation (since implementation package example apps are mostly not things we expect users to look at, so it's never been a priority):

• Removed the canLaunch/launch anti-pattern, which was long since removed from the app-facing package. This copies the code from app-facing example to demonstrate canLaunch controlling enabling a UI element, which is how we recommend using it.
• Removed all the configuration options that only ever worked on Android, since they are't relevant to an iOS example.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩² ↩³

[stuartmorgan-g]

Unlike the quick_actions case I could not find any good reason for this behavior. Unlike quick_actions it wasn't added later, but was just part of the very first url_launcher checkin, and I think of any reason this would be relevant for url_launcher testing, so I didn't replicate this into the Swift version, and just stuck with the standard template code.

[stuartmorgan-g]

Removed because they are no longer in the example app, because these options do nothing on iOS.

[gemini-code-assist]

Code Review

This pull request modernizes the url_launcher_ios example application, migrating the native iOS part from Objective-C to Swift and updating the Dart code to use the latest url_launcher APIs, such as launchUrl with LaunchOptions, while also demonstrating capability checks. A medium-severity vulnerability was identified where unsanitized user input is used to construct a tel: URI, which could lead to unintended behavior.