Rename MathKeyboardSwiftUI to MathKeyboardSwift

[maitbayev]

Motivation

• Standardize the keyboard module name by removing the redundant UI suffix and align type names and imports across the package and example project.

Description

• Renamed the Swift package product/target from MathKeyboardSwiftUI to MathKeyboardSwift in Package.swift and updated the target name accordingly.
• Moved and renamed source module directory Sources/MathKeyboardSwiftUI -> Sources/MathKeyboardSwift and migrated all keyboard sources and assets into the new module folder.
• Renamed the keyboard root view class and file from MTMathKeyboardSwiftUIRootView/MTMathKeyboardSwiftUIRootView.swift to MTMathKeyboardSwiftRootView/MTMathKeyboardSwiftRootView.swift and updated its API (sharedInstance() return type and internal references).
• Updated imports/usages in the example (ContentView.swift) to import MathKeyboardSwift and switched mathLabel.keyboard to use MTMathKeyboardSwiftRootView.sharedInstance(); updated Xcode project product references in project.pbxproj to the new product name.

Testing

• Ran swift test, which failed in this environment due to network restrictions when fetching the external dependency https://github.com/maitbayev/iosMath.git (CONNECT tunnel failed, HTTP 403), so package tests could not complete.

---

Codex Task