feat: add merchant user edit page with editable profile fields

- Add /admin/merchant-users/{id}/edit page route and template
- Replace toggle-status button with edit button on merchant-users list
- Editable fields: username, email, first name, last name
- Quick actions: toggle status, delete (with double confirm)
- Move RBAC two-phase plan to docs/proposals/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/tenancy/static/admin/js/merchant-users.js

@@ -16,10 +16,8 @@ function merchantUsersPage() {
         merchantUsers: [],
         loading: false,
         error: null,
-        showToggleStatusModal: false,
         showDeleteModal: false,
         showDeleteFinalModal: false,
-        userToToggle: null,
         userToDelete: null,
         filters: {
             search: '',
@@ -230,30 +228,6 @@ function merchantUsersPage() {
             }
         },
 
-        // Toggle user active status
-        async toggleUserStatus(user) {
-            const action = user.is_active ? 'deactivate' : 'activate';
-            merchantUsersLog.info(`Toggle status: ${action} for user`, user.username);
-
-            try {
-                const url = `/admin/users/${user.id}/status`;
-                window.LogConfig.logApiCall('PUT', url, null, 'request');
-
-                const response = await apiClient.put(url);
-
-                window.LogConfig.logApiCall('PUT', url, response, 'response');
-
-                user.is_active = response.is_active;
-                Utils.showToast(`User ${action}d successfully`, 'success');
-                merchantUsersLog.info(`User ${action}d successfully`);
-
-                await this.loadStats();
-            } catch (error) {
-                window.LogConfig.logError(error, `Toggle Status (${action})`);
-                Utils.showToast(error.message || `Failed to ${action} user`, 'error');
-            }
-        },
-
         // Intermediate step for double-confirm delete
         confirmDeleteStep() {
             merchantUsersLog.info('First delete confirmation accepted, showing final confirmation');