fix: resolve NameError in export_folder_link, secure RNG, and update deprecated mongo method

[Gaoc3]

Overview

This Pull Request addresses several bugs and deprecations discovered during a static analysis of the codebase.

Fixes Included

1. NameError & Logic Bug in export_folder_link.py

   • Crash Fix: Added the missing types import to prevent a NameError crash when types.ExportedFolderLink._parse(r) is called.
   • Logic Fix: Fixed a copy-paste error where folder.included_chats was mistakenly appended to the peers list for both excluded_chats and pinned_chats conditions.

2. Deprecation in mongo_storage.py

   • Fix: Replaced the deprecated remove({}) method with delete_many({}). remove() was removed in PyMongo v4.0+, causing silent failures within the try-except block when remove_peers=True is used.

3. Insecure RNG in prime.py

   • Security Fix: Replaced random.randint with the cryptographically secure secrets.randbelow for prime generation.

[codacy-production]

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