docs(tutorial): fix invalid nested Smarty delimiter syntax

Replace all <{if <{function}>}> nested delimiter patterns with the
correct assign-then-check pattern:
  <{function assign="var"}>
  <{if $var}>...<{/if}>

Fixes: is_user_logged_in, has_user_permission, user_has_role,
validate_email examples and quick reference table entry.

Author: mambax7

smarty4_plugins/TUTORIAL.md

@@ -70,15 +70,18 @@ Returns: `uid`, `uname`, `name`, `email`, `groups` (array), `is_admin` (bool).
 ### Check Login Status, Permissions, and Roles
 
 ```smarty
-<{* Boolean check *}>
-<{if <{is_user_logged_in}>}>
-    <{if <{has_user_permission permission="module_admin"}>}>
+<{* Assign results first, then use in conditionals *}>
+<{is_user_logged_in assign="logged_in"}>
+<{if $logged_in}>
+    <{has_user_permission permission="module_admin" assign="is_admin"}>
+    <{if $is_admin}>
         <a href="admin.php">Admin Panel</a>
     <{/if}>
 <{/if}>
 
 <{* Check XOOPS group membership (by group ID) *}>
-<{if <{user_has_role role="1"}>}>
+<{user_has_role role="1" assign="is_webmaster"}>
+<{if $is_webmaster}>
     <span class="badge">Webmaster</span>
 <{/if}>
 ```
@@ -258,7 +261,8 @@ For AJAX forms or cases where you need the token separately:
 ### Validate Email
 
 ```smarty
-<{if <{validate_email email=$userEmail}>}>
+<{validate_email email=$userEmail assign="is_valid"}>
+<{if $is_valid}>
     <p>Valid email</p>
 <{/if}>
 ```
@@ -815,7 +819,7 @@ Accepts arrays, objects, or JSON strings. Outputs with `JSON_PRETTY_PRINT | JSON
 | `xo_avatar` | `<{xo_avatar uid=$uid size=64}>` |
 | `xo_module_url` | `<{xo_module_url module="news" path="index.php"}>` |
 | `xo_debug` | `<{xo_debug var=$data label="Debug"}>` |
-| `is_user_logged_in` | `<{if <{is_user_logged_in}>}>` |
+| `is_user_logged_in` | `<{is_user_logged_in assign="logged"}>` then `<{if $logged}>` |
 | `has_user_permission` | `<{has_user_permission permission="view"}>` |
 | `form_open` / `form_close` | Auto CSRF token |
 | `form_input` | `<{form_input type="text" name="x" class="form-control"}>` |