Adds user settings for the Castle extension

Adds functionality to configure the Castle extension, including a wallet ID.

This allows administrators to customize the extension's behavior by specifying a dedicated wallet for castle operations.

templates/castle/index.html

@@ -11,8 +11,17 @@
   <div class="col-12 col-md-8 col-lg-7 q-gutter-y-md">
     <q-card>
       <q-card-section>
-        <h5 class="q-my-none">🏰 Castle Accounting</h5>
-        <p>Track expenses, receivables, and balances for the collective</p>
+        <div class="row items-center no-wrap">
+          <div class="col">
+            <h5 class="q-my-none">🏰 Castle Accounting</h5>
+            <p class="q-mb-none">Track expenses, receivables, and balances for the collective</p>
+          </div>
+          <div class="col-auto" v-if="isAdmin">
+            <q-btn flat round icon="settings" @click="showSettingsDialog">
+              <q-tooltip>Settings</q-tooltip>
+            </q-btn>
+          </div>
+        </div>
       </q-card-section>
     </q-card>
 
@@ -233,4 +242,32 @@
   </q-card>
 </q-dialog>
 
+<!-- Settings Dialog -->
+<q-dialog v-model="settingsDialog.show" position="top">
+  <q-card v-if="settingsDialog.show" class="q-pa-lg q-pt-xl lnbits__dialog-card">
+    <q-form @submit="submitSettings" class="q-gutter-md">
+      <div class="text-h6 q-mb-md">Castle Settings</div>
+
+      <q-input
+        filled
+        dense
+        v-model.trim="settingsDialog.castleWalletId"
+        label="Castle Wallet ID *"
+        placeholder="The wallet ID that represents the Castle"
+      ></q-input>
+
+      <div class="text-caption text-grey">
+        This wallet will be used for Castle operations and transactions.
+      </div>
+
+      <div class="row q-mt-lg">
+        <q-btn unelevated color="primary" type="submit" :loading="settingsDialog.loading">
+          Save Settings
+        </q-btn>
+        <q-btn v-close-popup flat color="grey" class="q-ml-auto">Cancel</q-btn>
+      </div>
+    </q-form>
+  </q-card>
+</q-dialog>
+
 {% endblock %}