Load role permissions when opening the Edit Role dialog

The dialog reads from rolePermissionsForView / roleUsersForView, but
editRole(role) only ever populated the form fields and showed the
dialog — those arrays were left at whatever state the rest of the page
had set them to. Result: opening Edit Role for a role with existing
permissions showed "No permissions assigned to this role yet", and the
list only "appeared" because adding a permission triggered a refresh.

Mirror viewRole's pattern: clear both arrays, GET /admin/roles/{id},
populate from the response, then show the dialog after $nextTick.

Closes #14

static/js/permissions.js

@@ -709,7 +709,7 @@ window.app = Vue.createApp({
       }
     },
 
-    editRole(role) {
+    async editRole(role) {
       this.editingRole = true
       this.selectedRole = role
       this.roleForm = {
@@ -717,6 +717,28 @@ window.app = Vue.createApp({
         description: role.description || '',
         is_default: role.is_default || false
       }
+      this.rolePermissionsForView = []
+      this.roleUsersForView = []
+
+      try {
+        const response = await LNbits.api.request(
+          'GET',
+          `/libra/api/v1/admin/roles/${role.id}`,
+          this.g.user.wallets[0].adminkey
+        )
+        this.rolePermissionsForView = [...(response.data.permissions || [])]
+        this.roleUsersForView = [...(response.data.users || [])]
+      } catch (error) {
+        console.error('Failed to load role details:', error)
+        this.$q.notify({
+          type: 'negative',
+          message: 'Failed to load role permissions',
+          caption: error.message || 'Unknown error',
+          timeout: 5000
+        })
+      }
+
+      await this.$nextTick()
       this.showCreateRoleDialog = true
     },