⚡ Bolt: Add stable keys to LazyColumn to optimize Compose re-renders

[editinghero]

💡 What: Added stable key identifiers to items(chatMessages), items(filteredHistory), and items(allNotes) within the AiAssistantBottomSheet component.
🎯 Why: Without keys, Jetpack Compose is forced to recompose every item in the LazyColumn when the list changes (e.g., when a new chat message arrives or the user filters history). This causes unnecessary UI churn and jank.
📊 Impact: Eliminates O(N) recompositions on list changes, reducing CPU overhead and improving scrolling performance. The UI will now only recompose the specific items that have changed.
🔬 Measurement: Use the Android Studio Layout Inspector or Compose Recomposition counters to observe reduced recomposition counts in the bottom sheet when new chat messages arrive.

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PR created automatically by Jules for task 13513607119182896091 started by @editinghero

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[editinghero]

Merged locally into main in commit aa1eaae with additional security hardening and biometric cleanup.