feat: add file storage settings and uploads

apps/web/src/styles/playground.css

@@ -63,6 +63,88 @@
   transform: rotate(-8deg);
 }
 
+.composerUpload:disabled {
+  cursor: not-allowed;
+  opacity: 0.58;
+}
+
+.composerUploadSpinner {
+  animation: composer-upload-spin 0.9s linear infinite;
+}
+
+.composerInputStack {
+  display: grid;
+  min-width: 0;
+  gap: 8px;
+}
+
+.composerUploadArea {
+  display: grid;
+  gap: 6px;
+}
+
+.composerUploadList {
+  display: flex;
+  min-width: 0;
+  flex-wrap: wrap;
+  gap: 6px;
+}
+
+.composerUploadChip {
+  display: inline-flex;
+  max-width: min(100%, 320px);
+  min-height: 28px;
+  align-items: center;
+  gap: 6px;
+  padding: 4px 7px;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-sm);
+  background: var(--surface-muted);
+  color: var(--text-normal);
+  font-size: var(--font-size-xs);
+}
+
+.composerUploadChip span {
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.composerUploadChip small {
+  flex: 0 0 auto;
+  color: var(--muted-foreground);
+}
+
+.composerUploadChip button {
+  display: grid;
+  width: 18px;
+  height: 18px;
+  place-items: center;
+  border: 0;
+  border-radius: 999px;
+  background: transparent;
+  color: var(--text-soft);
+  padding: 0;
+}
+
+.composerUploadChip button:hover {
+  background: var(--surface);
+  color: var(--text-normal);
+}
+
+.composerUploadMessage {
+  color: var(--muted-foreground);
+  font-size: var(--font-size-xs);
+  line-height: var(--line-height-relaxed);
+}
+
+@keyframes composer-upload-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
 .composerBody .shTextarea {
   min-height: 88px;
   border: 0;