feat(notes): share an always-latest link, not just a snapshot

The Share button now offers two links: the pinned snapshot (default) and
an "always latest" link that carries note paths in `?liveNotes` instead of
blob shas. On open they resolve to the current shas against the HEAD file
list and the URL is rewritten to the ordinary pinned form, so freshness,
editing and the snapshot banner keep working unchanged.

src/components/HeaderNote.vue

@@ -1,6 +1,7 @@
 <script lang="ts" setup>
 import FontChange from "@/components/FontChange.vue"
 import HomeButton from "@/components/HomeButton.vue"
+import ShareNote from "@/components/ShareNote.vue"
 
 defineProps<{ user: string; repo: string }>()
 </script>
@@ -55,6 +56,7 @@ defineProps<{ user: string; repo: string }>()
         <path d="M5 20l6 -16l2 0l7 16" />
       </svg>
     </button>
+    <share-note />
     <router-link
       class="btn btn-ghost btn-circle"
       :to="{ name: 'FluxNoteView', params: { user, repo } }"