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.

templates/castle/index.html

@@ -76,14 +76,17 @@
           </div>
         </div>
         <div v-if="balance !== null">
-          <div class="text-h4" :class="balance.balance >= 0 ? 'text-positive' : 'text-negative'">
+          <div class="text-h4" :class="balance.balance >= 0 ? 'text-negative' : 'text-positive'">
             {% raw %}{{ formatSats(Math.abs(balance.balance)) }} sats{% endraw %}
           </div>
-          <div class="text-subtitle2">
+          <div class="text-subtitle2" v-if="isSuperUser">
+            {% raw %}{{ balance.balance > 0 ? 'Total you owe' : balance.balance < 0 ? 'Total owed to you' : 'No outstanding balances' }}{% endraw %}
+          </div>
+          <div class="text-subtitle2" v-else>
             {% raw %}{{ balance.balance >= 0 ? 'Castle owes you' : 'You owe Castle' }}{% endraw %}
           </div>
           <q-btn
-            v-if="balance.balance < 0"
+            v-if="balance.balance < 0 && !isSuperUser"
             color="primary"
             class="q-mt-md"
             @click="showPayBalanceDialog"
@@ -98,6 +101,40 @@
       </q-card-section>
     </q-card>
 
+    <!-- User Balances Breakdown (Super User Only) -->
+    <q-card v-if="isSuperUser && allUserBalances.length > 0">
+      <q-card-section>
+        <h6 class="q-my-none q-mb-md">Outstanding Balances by User</h6>
+        <q-table
+          flat
+          :rows="allUserBalances"
+          :columns="[
+            {name: 'user', label: 'User ID', field: 'user_id', align: 'left'},
+            {name: 'balance', label: 'Amount Owed', field: 'balance', align: 'right'}
+          ]"
+          row-key="user_id"
+          hide-pagination
+          :rows-per-page-options="[0]"
+        >
+          <template v-slot:body-cell-user="props">
+            <q-td :props="props">
+              <div class="text-caption">{% raw %}{{ props.row.user_id.substring(0, 16) }}...{% endraw %}</div>
+            </q-td>
+          </template>
+          <template v-slot:body-cell-balance="props">
+            <q-td :props="props">
+              <div :class="props.row.balance > 0 ? 'text-negative' : 'text-positive'">
+                {% raw %}{{ formatSats(Math.abs(props.row.balance)) }} sats{% endraw %}
+              </div>
+              <div class="text-caption text-grey">
+                {% raw %}{{ props.row.balance > 0 ? 'You owe' : 'Owes you' }}{% endraw %}
+              </div>
+            </q-td>
+          </template>
+        </q-table>
+      </q-card-section>
+    </q-card>
+
     <!-- Quick Actions -->
     <q-card>
       <q-card-section>