feat: add S3-compatible storage provider (MinIO, Ceph, R2, etc.)

Adds a new 'S3-Compatible Storage' provider that works with any
S3-API-compatible object storage service, including MinIO, Ceph,
Cloudflare R2, Backblaze B2, and others.

Changes:
- New provider class: classes/providers/storage/s3-compatible-provider.php
  - Provider key: s3compatible
  - Reads user-configured endpoint URL from settings
  - Uses path-style URL access (required by most S3-compatible services)
  - Supports credentials via AS3CF_S3COMPAT_ACCESS_KEY_ID /
    AS3CF_S3COMPAT_SECRET_ACCESS_KEY wp-config.php constants
  - Disables AWS-specific features (Block Public Access, Object Ownership)
- New provider SVG icons (s3compatible.svg, -link.svg, -round.svg)
- Registered provider in main plugin class with endpoint setting support
- Updated StorageProviderSubPage to show endpoint URL input for S3-compatible
- Built pro settings bundle with rollup (Svelte 4.2.19)
- Added package.json and updated rollup.config.mjs for pro-only builds

vendor/Aws3/Aws/Credentials/CredentialsUtils.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Credentials;
+
+final class CredentialsUtils
+{
+    /**
+     * Determines whether a given host
+     * is a loopback address.
+     *
+     * @param $host
+     *
+     * @return bool
+     */
+    public static function isLoopBackAddress($host) : bool
+    {
+        if (!\filter_var($host, \FILTER_VALIDATE_IP)) {
+            return \false;
+        }
+        if (\filter_var($host, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV6)) {
+            if ($host === '::1') {
+                return \true;
+            }
+            return \false;
+        }
+        $loopbackStart = \ip2long('127.0.0.0');
+        $loopbackEnd = \ip2long('127.255.255.255');
+        $ipLong = \ip2long($host);
+        return $ipLong >= $loopbackStart && $ipLong <= $loopbackEnd;
+    }
+}