refactor: introduce event-driven page completion handling

[theEvilReaper]

Proposed changes

This pull request overhauls how the game handles the case where all pages are found. An event is now fired instead of relying on method references, and the old approach has been removed

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING.md
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

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