Add Far Manager-style F9 menu, license CI, search dialog z-fix

[bluestreak01]

Summary

• F9 menu system: Far Manager-style dropdown menu bar with five categories (Left, File, Command, Options, Right) that organizes all shortcuts into a discoverable hierarchy. Supports keyboard navigation (arrows, Enter, Esc) and mouse clicks on both the menu bar and dropdown items. Left/Right menus show current sort mode with a • indicator and allow setting sort per-panel directly. Sort cycling moves to Ctrl+F9.
• License CI check: Adds cargo-deny license checking to CI via deny.toml, ensuring all dependencies remain Apache-2.0 compatible.
• Search dialog z-order fix: Moves Ctrl+S file search dialog rendering after bottom panels (CI, diff, shell, Claude, SSH) so it draws on top instead of being painted over.
• Dark theme contrast: Bumps QuestDB Dark theme selection background from rgb(46,39,64) to rgb(74,50,100) for better highlight visibility in menus and dialogs.

New files

• src/ui/menu.rs — menu data, rendering, click detection, sort indicator, 14 tests
• deny.toml — cargo-deny license allowlist

Changed files

• src/action.rs — new OpenMenu, SortByName/Size/Date(side) actions
• src/app.rs — MenuState, key/mouse interception, action dispatch
• src/panel/mod.rs — set_sort(field) method
• src/ui/mod.rs — menu overlay rendering, search dialog z-order fix
• src/ui/footer.rs — F9 label: Sort → Menu
• src/ui/help_dialog.rs — F9 → Menu in Application section, Ctrl+F9 → sort in File Operations
• src/theme.rs — dark theme selection bg contrast bump
• .github/workflows/ci.yml — license check job

Test plan

• F9 opens menu bar, Esc/F9 closes it
• Arrow keys navigate categories and items, Enter executes
• Mouse click on menu titles opens/switches/closes menus
• Mouse click on dropdown items executes the action
• Click outside menu dismisses it
• Left/Right menus show • on current sort, selecting a sort changes it
• Ctrl+F9 still cycles sort (name → size → date)
• Ctrl+S search dialog renders on top of CI/shell panels
• Dark theme: menu highlight is clearly visible
• cargo deny check licenses passes
• cargo test — 900 tests pass (14 new menu tests)

🤖 Generated with Claude Code