Add Cmd+Enter keyboard shortcut to trigger generation

[Dumebii]

Expected behaviour

When focus is inside the main input textarea on the dashboard, pressing Cmd+Enter (Mac) or Ctrl+Enter (Windows/Linux) should trigger generation — same as clicking the Generate button.

Implementation

Find the textarea component in the dashboard and attach a keydown handler:

if ((e.metaKey || e.ctrlKey) && e.key === 'Enter') {
  e.preventDefault();
  handleGenerate();
}

Acceptance criteria

• Cmd+Enter triggers generation from the textarea
• Does not interfere with normal Enter (new line) behaviour
• Works on Mac (metaKey) and Windows/Linux (ctrlKey)
• Does not double-submit if the button is clicked at the same time
• Button shows loading state the same way a click does

This is roughly a 10-line change. Good first issue.