add keepass2android offline google play link in readme

[mrsruj]

📝 Description

🔗 Related Issue

🛠️ Type of Change

• Bug fix (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

✅ Checklist

Before submitting this PR, please confirm the following:

• My code follows the style guidelines of this project.
• I have performed a self-review of my own (or any AI generated) code.
• I have added/updated tests that prove my fix is effective or that my feature works.
• All new and existing tests passed locally.
• I have commented my code, particularly in hard-to-understand areas.
• I have built the app locally, verified that it builds and tested the changes thoroughly.

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📸 Screenshots/Videos (if applicable)