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/backend/src/migrations/0001_is_admin.sql

@@ -0,0 +1,3 @@
+ALTER TABLE "users" ADD COLUMN "is_admin" boolean NOT NULL DEFAULT false;--> statement-breakpoint
+UPDATE "users" SET "is_admin" = true WHERE "role" = 'admin';--> statement-breakpoint
+UPDATE "users" SET "role" = 'viewer' WHERE "role" = 'admin';

packages/backend/src/migrations/meta/_journal.json

@@ -8,6 +8,13 @@
       "when": 1772645674513,
       "tag": "0000_pale_hellion",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "7",
+      "when": 1772645674514,
+      "tag": "0001_is_admin",
+      "breakpoints": true
     }
   ]
 }