🎨 Palette: Add tooltips to icon-only buttons

[NotEduCo342]

💡 What: Added tooltip properties to multiple IconButton widgets across the application, specifically the "Send message" button in ChatScreen and the "Clear search" buttons in UserSearchScreen and GroupDiscoverScreen.
🎯 Why: Icon-only buttons without tooltips lack context for mouse users (on hover/long-press) and are not adequately described by screen readers. Adding tooltips improves both UX and accessibility.
♿ Accessibility: Improved screen reader support by providing descriptive labels for these actionable icons.

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PR created automatically by Jules for task 8499664984701069284 started by @NotEduCo342

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