🔒 Fix Unhandled Unwrap Risk in UI Buttons

[dynamikdev]

🎯 What: The vulnerability fixed was several unsafe unwrap() calls on array indices in Bevy UI interaction systems within src/ui/systems.rs.
⚠️ Risk: A Denial of Service (DoS) could occur if a UI interaction event happened where a button unexpectedly lost its child (e.g., text node removed or query failed). This would result in an unhandled panic and crash the entire application.
🛡️ Solution: The unsafe children[0] indexing and unwrap() calls were replaced with defensive let else patterns (children.first() and text_query.get_mut(child)) which gracefully skip the logic if the required child or Text component is not present, rather than crashing.

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PR created automatically by Jules for task 14822055852122451628 started by @dynamikdev

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