chore: Release 5.5.6

[onesignal-deploy]

Channels: Current

🐛 Bug Fixes

• fix: [SDK-4722] guard getNotifications() in onDetachedFromEngine ([Bug]: Android Crash on app destroy: IllegalStateException: Must call 'initWithContext' before use (Regression in OneSignal-Android-SDK 5.9.2) #1149) (fix: [SDK-4722] guard getNotifications() in onDetachedFromEngine (#1149) #1150)

[claude]

Straightforward release bump to 5.5.6 — all version strings updated consistently across pubspec, gradle, podspec, and SDK version constants.

Extended reasoning...

Overview

This PR bumps the SDK version from 5.5.5 to 5.5.6 across the standard set of release artifacts: pubspec.yaml, android/build.gradle, ios/onesignal_flutter.podspec, and the SDK version constants embedded in OneSignalPlugin.java (050506) and OneSignalPlugin.m (050506). No logic changes are included — the underlying bug fix referenced in the description (#1150, SDK-4722) was already merged separately and is just being released here.

Security risks

None. This is purely a version-string bump with no changes to authentication, permissions, networking, crypto, or input handling.

Level of scrutiny

Minimal scrutiny is appropriate. Release-version-bump PRs are the canonical mechanical change — values are easy to verify, and the only meaningful check is that all five version strings are consistent, which they are (5.5.6 / 050506).

Other factors

The Android dependency (com.onesignal:OneSignal:5.9.2) and iOS dependency (OneSignalXCFramework 5.5.1) are unchanged from the prior release, so no transitive risk is introduced. No reviewer comments are outstanding, and the bug hunting system found no issues.