🔒 Fix unhandled unwrap panic risks in UI button queries

[dynamikdev]

🎯 What: Replaced unhandled unwrap() calls when retrieving Text components from button children in src/ui/systems.rs.
⚠️ Risk: If a UI button entity lacks children or its first child lacks a Text component, the application would panic, leading to a Denial of Service (DoS) and application crash.
🛡️ Solution: Used safe let-else patterns (children.first() and text_query.get_mut()) to cleanly skip entities that do not match expectations, preventing panics and ensuring runtime stability.

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PR created automatically by Jules for task 148543548107825725 started by @dynamikdev

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