Adds super user balance overview

Implements functionality for super users to view a breakdown of outstanding balances for all users.

This includes:
- Adding an API endpoint to fetch all user balances.
- Updating the frontend to display these balances in a table, accessible only to super users.
- Modifying the balance calculation for the current user to reflect the total owed by or to the castle for super users.

This provides super users with a comprehensive view of the castle's financial position.

static/js/index.js

@@ -8,6 +8,7 @@ window.app = Vue.createApp({
   data() {
     return {
       balance: null,
+      allUserBalances: [],
       transactions: [],
       accounts: [],
       currencies: [],
@@ -71,10 +72,27 @@ window.app = Vue.createApp({
           this.g.user.wallets[0].inkey
         )
         this.balance = response.data
+
+        // If super user, also load all user balances
+        if (this.isSuperUser) {
+          await this.loadAllUserBalances()
+        }
       } catch (error) {
         LNbits.utils.notifyApiError(error)
       }
     },
+    async loadAllUserBalances() {
+      try {
+        const response = await LNbits.api.request(
+          'GET',
+          '/castle/api/v1/balances/all',
+          this.g.user.wallets[0].adminkey
+        )
+        this.allUserBalances = response.data
+      } catch (error) {
+        console.error('Error loading all user balances:', error)
+      }
+    },
     async loadTransactions() {
       try {
         const response = await LNbits.api.request(