feel: card resting spacing + editor Cmd/Ctrl+Enter

- NoteCard: overlay the hover toolbar (absolute bottom-right, translucent
  backdrop, pointer-events gated) instead of reserving a permanent action row.
  At rest cards are now content-sized with even padding, so text no longer
  looks pinned to the top above an empty strip. Affects every card surface
  (board, search, graph, reminders).
- NoteEditor: Cmd/Ctrl+Enter saves & closes (mirrors Esc-closes).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/NoteEditor.vue

@@ -182,6 +182,8 @@ async function act(fn: () => Promise<void>) {
       role="dialog"
       aria-modal="true"
       @keydown.esc="close"
+      @keydown.enter.meta.prevent="close"
+      @keydown.enter.ctrl.prevent="close"
       @paste="onPaste"
     >
       <div class="flex flex-col gap-2 p-4">