Fix iOS view controller initialization and ownership

[tryk016]

The iOS view controller initializer currently skips [super init], and its viewDidLoad override does not call the superclass implementation. The app delegate also keeps the +1 ownership returned by [ViewController new] after assigning it to the retaining rootViewController property.

Use the normal UIKit initialization chain, call [super viewDidLoad] and balance the temporary controller ownership after assignment. Rename the fullscreen setter argument to avoid shadowing the ivar.

Validation:

• Release builds pass for iPhoneOS arm64 and iPhone Simulator arm64 at iOS 15.0
• Clang static analysis is clean for the controller initialization and ownership path
• the integrated build starts, backgrounds and resumes successfully on an iPhone 15 Pro Max