feat(ios): add Swift Package Manager support

[TeddyYeung]

Why

Flutter 3.27+ makes Swift Package Manager (SPM) the default for iOS builds. CocoaPods trunk will be read-only from December 2, 2026. Plugins without SPM support will require users to pass --no-enable-swift-package-manager on every build.

This PR adds iOS SPM support to freerasp so it works seamlessly with modern Flutter toolchains.

What changed

• Added ios/freerasp/Package.swift — SPM manifest (swift-tools-version 5.9, iOS 12.0)
• Added ios/freerasp/TalsecRuntime.xcframework — symlink to local binary target (mirrors existing ios/TalsecRuntime.xcframework)
• Added ios/freerasp/Sources/freerasp/ — Swift-only SPM target (mirrors Classes/ Swift files)
• Updated ios/freerasp.podspec — iOS platform 8.0 → 12.0
• Updated pubspec.yaml — iOS pluginClass: SwiftFreeraspPlugin (direct Swift registration for SPM)
• Updated CHANGELOG.md — 8.0.1 entry
• Updated .gitignore — added .build/ and .swiftpm/

Architecture note

SPM does not support mixed-language targets (ObjC + Swift in the same target). The solution:

• SPM target: Swift files only (Sources/freerasp/) + TalsecRuntime as a local binaryTarget
• CocoaPods: uses existing ios/Classes/ with ObjC wrapper + Swift + vendored_frameworks (unchanged)
• TalsecRuntime.xcframework is already bundled in the repository — no remote download required

Testing

• ✅ flutter config --enable-swift-package-manager && flutter build ios --no-codesign — Build succeeded
• ✅ flutter config --no-enable-swift-package-manager && flutter build ios --no-codesign — Build succeeded

Tested with Flutter 3.35.7 on macOS.

Breaking Changes

None. CocoaPods behavior is unchanged.

References

• Flutter SPM guide: https://docs.flutter.dev/packages-and-plugins/swift-package-manager/for-plugin-authors