Add Command Palette (Cmd+K)

Summary

Add a global command palette to the app, opened with Cmd+K (or Ctrl+K on Windows and Linux). It lets the user jump to any page, run common actions, and pull up recent items without leaving the keyboard.

Implementation Changes

• Add the palette component in src/components/command-palette.tsx:
  • Mount it at the root so it overlays any route.
  • Render through a portal so it sits above existing dialogs.
• Wire the global hotkey in src/hooks/use-command-palette.ts:
  • Listen for Cmd+K and Ctrl+K and toggle the palette open.
  • Skip the shortcut when focus is inside an input or contenteditable.
• Register actions in src/lib/commands.ts:
  • Pull navigation entries from the existing route manifest.
  • Let feature modules register their own commands at boot.
• Surface recent items from the activity log:
  • Read the last 10 viewed items from local storage and put them at the top.
  • Update the log whenever a route view is recorded.

Acceptance

• Cmd+K opens and closes the palette from anywhere in the app.
• Typing filters navigation, actions, and recent items in a single list.
• The first match is preselected and Enter triggers it.
• Esc closes the palette and returns focus to the previously focused element.