Fix paste counting and panel interaction delays

[uniplanck]

Changes

• restore regular Cmd+V usage counting with permission-aware event monitoring
• add Settings sidebar hover feedback and vertically center Search
• change Open Board-Man default to Command+Option+V with safe legacy-default migration
• cache panel data and avoid repeated Snippets reloads
• move screenshot metadata query off the main thread

Verification

• 41 local tests passed
• arm64 Release build installed and signed
• runtime Cmd+V detection and count increment confirmed
• history reconstruction reduced from about 1.4s to 16-31ms