fix: add @babel/plugin-syntax-import-assertions for AdminJS build

AdminJS requires this Babel plugin during the Astro build step.
Without it, Rollup fails to process .adminjs/entry.js.

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

package.json

@@ -35,6 +35,7 @@
     "tslib": "^2.8.1"
   },
   "devDependencies": {
+    "@babel/plugin-syntax-import-assertions": "^7.28.6",
     "@types/bcrypt": "^6.0.0",
     "@types/node": "^25.3.0",
     "prisma": "^6.19.2"

pnpm-lock.yaml

@@ -70,6 +70,9 @@ importers:
         specifier: ^2.8.1
         version: 2.8.1
     devDependencies:
+      '@babel/plugin-syntax-import-assertions':
+        specifier: ^7.28.6
+        version: 7.28.6(@babel/core@7.29.0)
       '@types/bcrypt':
         specifier: ^6.0.0
         version: 6.0.0