feat(profile): circle action buttons, tighter tabs, quoted note navigation

[dmnyc]

Summary

• Replace Follow/Mute/DM/Zap profile buttons with uniform 40dp circle Surface icons (iOS-style action bar)
• Add Mute/Unmute button to profile header with VolumeOff/VolumeUp icons
• Fix quoted note tap-through: outer PostCard uses Final-pass pointer detection so tapping an embedded quoted note opens its thread view
• Wire NoteActions.onProfileClick so tapping an author avatar inside a quoted/embedded note navigates to their profile directly
• Fix repost card original-author avatar to navigate to their profile
• Replace M3 Tab composable (90dp min-width enforced) with plain Box + clickable for text-proportional tab widths and a custom narrow indicator underline — eliminates uneven tab spacing
• Add transparent spacer and right-side gradient fade below sticky tab bar
• Add "no replies" empty state illustration to ThreadScreen
• Wire mute action through Navigation → FeedViewModel.blockUser

Test plan

• View another user's profile — confirm 4 circle icon buttons (DM, Zap, Follow, Mute) are uniform size and style
• Tap Follow/Unfollow and Mute/Unmute — confirm state toggles correctly
• Open a note with an embedded quoted note — confirm tapping the quoted card opens its thread view
• Tap the author avatar inside a quoted note — confirm it navigates to that author's profile
• View a repost card — confirm tapping the original author's avatar navigates to their profile
• Profile page tab bar — confirm tabs are proportional to text width with consistent spacing
• Open a thread with no replies — confirm empty state illustration appears

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