feat(messaging-ui): Gmail-style uploading chip while an attachment uploads (0.1.2)

Picking a file now shows an immediate chip with the filename + a spinner while
the bytes upload (mail compose, mail reply, and the messenger composer), instead
of only appearing once upload finishes. Respects prefers-reduced-motion.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/iios-messaging-ui/src/styles.css

@@ -368,6 +368,25 @@ button.miu-attach-dl:hover {
   align-items: center;
   gap: 6px;
 }
+.miu-attach-chip.is-uploading,
+.miu-staged.is-uploading {
+  color: var(--miu-muted);
+}
+.miu-spinner {
+  display: inline-block;
+  width: 12px;
+  height: 12px;
+  border: 2px solid var(--miu-border);
+  border-top-color: var(--miu-accent);
+  border-radius: 50%;
+  animation: miu-spin 0.7s linear infinite;
+}
+@keyframes miu-spin {
+  to { transform: rotate(360deg); }
+}
+@media (prefers-reduced-motion: reduce) {
+  .miu-spinner { animation-duration: 2s; }
+}
 .miu-attach-x {
   border: none;
   background: none;