feat(wpmc S3): procedural wpmc_* API + smoke test

Also fixes PluginBootTest to be order-independent (reset booted flag)
and to expect ShortcodeDmr hook that boot() now wires.

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

includes/wpmc-functions.php

@@ -0,0 +1,32 @@
+<?php
+declare(strict_types=1);
+
+use WPMultiCity\Helpers;
+
+if (!function_exists('wpmc_current_town')) {
+    function wpmc_current_town(): ?string
+    {
+        return Helpers::current_town();
+    }
+}
+
+if (!function_exists('wpmc_get_term_by_slug')) {
+    function wpmc_get_term_by_slug(string $slug, string $taxonomy = 'town'): ?\WP_Term
+    {
+        return Helpers::get_term_by_slug($slug, $taxonomy);
+    }
+}
+
+if (!function_exists('wpmc_alt_get_field')) {
+    function wpmc_alt_get_field(string $selector, $post_id = false, bool $format_value = true)
+    {
+        return Helpers::alt_get_field($selector, $post_id, $format_value);
+    }
+}
+
+if (!function_exists('wpmc_remove_domain_link')) {
+    function wpmc_remove_domain_link(string $url): string
+    {
+        return Helpers::remove_domain_link($url);
+    }
+}