refactor: add migration, seed permissions, update permissions API

feat(notes): add XLSX import island and admin route

feat(upload): add drag‑and‑drop upload, template download, UI tweaks

static/styles/ui.css

@@ -6,7 +6,6 @@
 
 .page-content {
   padding: 1.5rem;
-  max-width: 960px;
 }
 
 .page-title {
@@ -783,6 +782,70 @@
   text-decoration: underline;
 }
 
+/* -------------------------------------------------------
+   File drop zone (import pages)
+------------------------------------------------------- */
+
+.drop-zone {
+  border: 2px dashed
+    light-dark(var(--light-foreground-dimmer), var(--dark-foreground-dimmer));
+  border-radius: 6px;
+  background: light-dark(white, #141228);
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 0.6rem;
+  padding: 3rem 2rem;
+  cursor: pointer;
+  transition: border-color 150ms, background 150ms;
+  margin-bottom: 1.25rem;
+  text-align: center;
+}
+
+.drop-zone:hover,
+.drop-zone.dragging {
+  border-color: light-dark(var(--light-accent-color), var(--dark-accent-color));
+  background: light-dark(#f0fff4, #0a1a10);
+}
+
+.drop-zone-icon {
+  font-size: 2.4rem;
+  line-height: 1;
+  opacity: 0.8;
+}
+
+.drop-zone-text {
+  font-size: 0.88rem;
+  font-weight: var(--font-weight-bold);
+}
+
+.drop-zone-hint {
+  font-size: 0.75rem;
+  font-family: monospace;
+  color: light-dark(var(--light-foreground-dim), var(--dark-foreground-dim));
+}
+
+.drop-zone-file {
+  font-size: 0.78rem;
+  font-family: monospace;
+  color: light-dark(var(--light-accent-color), var(--dark-accent-color));
+  font-weight: var(--font-weight-bold);
+}
+
+.upload-actions {
+  display: flex;
+  gap: 0.75rem;
+  align-items: center;
+  margin-bottom: 0.75rem;
+}
+
+.upload-format {
+  font-size: 0.72rem;
+  font-family: monospace;
+  color: light-dark(var(--light-foreground-dim), var(--dark-foreground-dim));
+}
+
 /* Info note box */
 .info-note {
   padding: 0.75rem 1rem;