feat(toast): message toast opens the related chat + has a close icon (#33)

- Add a close (X) button to the message toast (closeToast, @click.stop) like the
  system notifications.
- Carry the sender pubkey on the toast; clicking now deep-links to that
  conversation (/dashboard/mesh?peer=<pubkey>) instead of the generic mesh page.
- Mesh.vue reads ?peer= on mount and opens the matching peer (by pubkey_hex/did),
  gracefully falling back to the mesh list when no match (B1/B2 identity).

type-check clean; useMessageToast tests 11/11.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/App.vue

@@ -59,6 +59,15 @@
               <p class="mt-0.5 text-sm text-white/70 line-clamp-2">{{ toastMessage.text }}</p>
               <p class="mt-1 text-xs text-orange-400">Click to view</p>
             </div>
+            <button
+              @click.stop="messageToast.closeToast"
+              aria-label="Dismiss notification"
+              class="-mt-1 -mr-1 shrink-0 rounded-full p-1 text-white/40 transition-colors hover:bg-white/10 hover:text-white/80"
+            >
+              <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12" />
+              </svg>
+            </button>
           </div>
         </div>
       </Transition>