Set default permission type to 'submit_expense' in grant forms

Changed default permission type from 'read' to 'submit_expense' in
all permission grant forms, as this is the most common use case when
Castle admins grant permissions to users.

Changes:
- grantForm initialization (line 31): 'read' → 'submit_expense'
- bulkGrantForm initialization (line 42): 'read' → 'submit_expense'
- resetGrantForm() method (line 315): 'read' → 'submit_expense'
- resetBulkGrantForm() method (line 402): 'read' → 'submit_expense'

Rationale: Most users need to submit expenses to their assigned
accounts, making 'submit_expense' a more practical default than
'read'. Admins can still select other permission types from the
dropdown if needed.

Affected: static/js/permissions.js

Co-Authored-By: Claude <noreply@anthropic.com>

static/js/permissions.js

@@ -28,7 +28,7 @@ window.app = Vue.createApp({
       grantForm: {
         user_id: '',
         account_id: '',
-        permission_type: 'read',
+        permission_type: 'submit_expense',
         notes: '',
         expires_at: ''
       },
@@ -39,7 +39,7 @@ window.app = Vue.createApp({
       bulkGrantForm: {
         user_ids: [],
         account_id: '',
-        permission_type: 'read',
+        permission_type: 'submit_expense',
         notes: '',
         expires_at: ''
       },
@@ -312,7 +312,7 @@ window.app = Vue.createApp({
       this.grantForm = {
         user_id: '',
         account_id: '',
-        permission_type: 'read',
+        permission_type: 'submit_expense',
         notes: '',
         expires_at: ''
       }
@@ -399,7 +399,7 @@ window.app = Vue.createApp({
       this.bulkGrantForm = {
         user_ids: [],
         account_id: '',
-        permission_type: 'read',
+        permission_type: 'submit_expense',
         notes: '',
         expires_at: ''
       }