Fix: Handle UTF-8 decode error and overflow error in wallet storage

[krishnakant2607]

I've fixed two issues in the wallet storage handling:

• A UnicodeDecodeError that occurs when reading wallet files with invalid UTF-8 encoding
• An OverflowError that happens when trying to display large error messages

The changes include:

• Better exception handling for UTF-8 decode errors in storage.py
• Added size limit checks to prevent overflow when displaying error messages
• More user-friendly error messages
• Graceful fallback for oversized error messages

Changed files:

1. electrum/storage.py
2. electrum/gui/qt/wizard/wallet.py

[SomberNight]

is this LLM-generated?