Fix iOS crash: sanitize forwarded event params before JSON serialization

[bilck]

Summary

toJsonString in the iOS bridge can crash the app with an uncaught Objective-C NSException when a forwarded event carries a non-JSON-serializable param value.

Crash

*** Terminating app due to uncaught exception 'NSInvalidArgumentException',
    reason: 'Invalid type in JSON write (__SwiftValue)'
  sendToUnity(method:data:)
  SuperwallDelegate.handleSuperwallEvent(withInfo:)
  SuperwallKit Superwall.track
  DeviceHelper.getEnrichment
  IdentityManager.identify(userId:options:)

Root cause

serializeEventInfo copies the native SuperwallEventInfo.params verbatim into the payload that sendToUnity passes to JSONSerialization.data(withJSONObject:). When a param value is not a JSON-native type (a Swift enum/struct/URL bridged as __SwiftValue), JSONSerialization raises an Objective-C NSInvalidArgumentException. That is an NSException, not a Swift Error, so the try? in toJsonString does not catch it and the app hard-crashes.

Reproduction

Deterministic on iOS at launch: after Superwall.Identify(...), the SDK runs getEnrichment and tracks an event whose params carry such a value; the delegate forwards it via handleSuperwallEvent → sendToUnity and the app terminates. Verified on iPad, iOS 26.5, Unity IL2CPP, SDK 0.2.4.

Fix

Route toJsonString through a recursive sanitizer that coerces any non-JSON leaf to its String(describing:) form, and guard with isValidJSONObject so residual edge cases (e.g. non-finite Doubles) drop the message instead of crashing. This protects the entire native→Unity path, not just event forwarding, and is a no-op for already-valid payloads.

Notes

• There is currently no SuperwallOptions flag to disable/filter event forwarding, and dropping the delegate is not viable for integrators who rely on it for entitlements — so guarding the bridge is the appropriate layer.
• Alternative considered: wrapping JSONSerialization in an Objective-C @try/@catch. Sanitizing up front was chosen because it preserves the payload (as strings) instead of dropping the whole message, and keeps everything in Swift.