feat: refactor agent manager, media library, and player UX

- Split admin users page into player/tier-1/tier-2 tabs with affiliation labels and context-specific create dialogs

- Add media library with uploaded_files migration, list/delete unused files API, and admin nav route

- Enforce player username format (alphanumeric 3-32) on frontend and backend via shared package

- Improve admin dialog/panel styling; refine player parlay and match bet card kickoff display

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/admin/src/layouts/ManageLayout.vue

@@ -22,6 +22,7 @@ const adminMenus = computed(() => [
   { path: '/cashback', label: t('nav.cashback') },
   { path: '/bets', label: t('nav.bets') },
   { path: '/contents', label: t('nav.contents') },
+  { path: '/media', label: t('nav.media') },
   { path: '/audit', label: t('nav.audit') },
   { path: '/smoke-tests', label: t('nav.smoke_tests') },
 ]);
@@ -175,6 +176,7 @@ watch(() => route.path, () => {
             </nav>
             <span v-else class="topbar-page-label">{{ currentLabel }}</span>
           </div>
+          <div id="topbar-page-actions" class="topbar-page-actions" />
         </div>
         <div class="topbar-right">
           <div class="user-chip">
@@ -390,6 +392,17 @@ watch(() => route.path, () => {
   box-shadow: 0 0 8px rgba(47, 181, 106, 0.45);
 }
 
+.topbar-page-actions {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  flex-shrink: 0;
+  margin-left: 8px;
+}
+.topbar-page-actions:empty {
+  display: none;
+}
+
 .topbar-right {
   display: flex; align-items: center; gap: 12px;
   flex-shrink: 0;