feat: refactor role system to is_admin flag, add Badge component, fix native dialogs

- Separate admin identity from role: viewer|model + is_admin boolean flag
- DB migration 0001_is_admin: adds column, migrates former admin role users
- Update ACL helpers, auth session, GraphQL types and all resolvers
- Admin layout guard and header links check is_admin instead of role
- Admin users table: show Admin badge next to name, remove admin from role select
- Admin user edit page: is_admin checkbox toggle
- Install shadcn Badge component; use in admin users table
- Fix duplicate photo keys in adminGetUser resolver
- Replace confirm() in /me recordings with Dialog component

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/admin/users/+page.svelte

@@ -8,6 +8,7 @@
   import { Button } from "$lib/components/ui/button";
   import { Input } from "$lib/components/ui/input";
   import { Select, SelectContent, SelectItem, SelectTrigger } from "$lib/components/ui/select";
+  import { Badge } from "$lib/components/ui/badge";
   import * as Dialog from "$lib/components/ui/dialog";
   import type { User } from "$lib/types";
 
@@ -22,7 +23,7 @@
 
   const currentUserId = page.data.authStatus?.user?.id;
 
-  const roles = ["", "viewer", "model", "admin"] as const;
+  const roles = ["", "viewer", "model"] as const;
 
   function debounceSearch(value: string) {
     clearTimeout(searchTimeout);
@@ -144,7 +145,12 @@
                   </div>
                 {/if}
                 <div class="min-w-0">
-                  <span class="font-medium block truncate">{user.artist_name || user.first_name || "—"}</span>
+                  <div class="flex items-center gap-1.5">
+                    <span class="font-medium truncate">{user.artist_name || user.first_name || "—"}</span>
+                    {#if user.is_admin}
+                      <Badge variant="default" class="shrink-0 text-[10px] px-1.5 py-0">Admin</Badge>
+                    {/if}
+                  </div>
                   <span class="text-xs text-muted-foreground sm:hidden truncate block">{user.email}</span>
                 </div>
               </div>
@@ -163,7 +169,6 @@
                 <SelectContent>
                   <SelectItem value="viewer">Viewer</SelectItem>
                   <SelectItem value="model">Model</SelectItem>
-                  <SelectItem value="admin">Admin</SelectItem>
                 </SelectContent>
               </Select>
             </td>