fix: extract data array from Metabase response

Metabase API returns {data: [...], total: number} instead of
a direct array. Update databases endpoint to extract and return
only the data array for easier frontend consumption.

Verified working with:
- facturador supabase (PostgreSQL, ID: 2)
- Sample Database (H2, ID: 1)

nuxt4-app/server/api/metabase/databases.get.ts

@@ -3,8 +3,15 @@
  */
 export default defineEventHandler(async (event) => {
   try {
-    const databases = await getMetabaseDatabases()
-    return databases
+    const response = await getMetabaseDatabases()
+
+    // Metabase returns {data: [...], total: number}
+    // Extract the data array
+    if (response && typeof response === 'object' && 'data' in response) {
+      return response.data
+    }
+
+    return response
   } catch (error: any) {
     console.error('[API] Failed to get Metabase databases:', error)
     throw createError({