Enables user selection for permissions

Replaces the user ID input field with a user selection dropdown,
allowing administrators to search and select users for permission
management. This simplifies the process of assigning permissions
and improves user experience.

Fetches Castle users via a new API endpoint and filters them
based on search input. Only users with Castle accounts
(receivables, payables, equity, or permissions) are listed.

static/js/permissions.js

@@ -5,6 +5,8 @@ window.app = Vue.createApp({
     return {
       permissions: [],
       accounts: [],
+      users: [],
+      filteredUsers: [],
       loading: false,
       granting: false,
       revoking: false,
@@ -48,6 +50,15 @@ window.app = Vue.createApp({
       }))
     },
 
+    userOptions() {
+      const users = this.filteredUsers.length > 0 ? this.filteredUsers : this.users
+      return users.map(user => ({
+        id: user.id,
+        username: user.username || user.id,
+        label: user.username ? `${user.username} (${user.id.substring(0, 8)}...)` : user.id
+      }))
+    },
+
     isGrantFormValid() {
       return !!(
         this.grantForm.user_id &&
@@ -130,6 +141,48 @@ window.app = Vue.createApp({
       }
     },
 
+    async loadUsers() {
+      if (!this.isSuperUser) {
+        return
+      }
+
+      try {
+        const response = await LNbits.api.request(
+          'GET',
+          '/castle/api/v1/admin/castle-users',
+          this.g.user.wallets[0].adminkey
+        )
+        this.users = response.data || []
+        this.filteredUsers = []
+      } catch (error) {
+        console.error('Failed to load users:', error)
+        this.$q.notify({
+          type: 'negative',
+          message: 'Failed to load users',
+          caption: error.message || 'Unknown error',
+          timeout: 5000
+        })
+      }
+    },
+
+    filterUsers(val, update) {
+      if (val === '') {
+        update(() => {
+          this.filteredUsers = []
+        })
+        return
+      }
+
+      update(() => {
+        const needle = val.toLowerCase()
+        this.filteredUsers = this.users.filter(user => {
+          const username = user.username || ''
+          const userId = user.id || ''
+          return username.toLowerCase().includes(needle) || userId.toLowerCase().includes(needle)
+        })
+      })
+    },
+
     async grantPermission() {
       if (!this.isGrantFormValid) {
         this.$q.notify({
@@ -283,7 +336,10 @@ window.app = Vue.createApp({
     if (this.g.user.wallets && this.g.user.wallets.length > 0) {
       await this.loadAccounts()
       if (this.isSuperUser) {
-        await this.loadPermissions()
+        await Promise.all([
+          this.loadPermissions(),
+          this.loadUsers()
+        ])
       }
     }
   }