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/GuzzleHttp/Psr7/UriComparator.php

@@ -0,0 +1,43 @@
+<?php
+
+declare (strict_types=1);
+namespace DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\UriInterface;
+/**
+ * Provides methods to determine if a modified URL should be considered cross-origin.
+ *
+ * @author Graham Campbell
+ */
+final class UriComparator
+{
+    /**
+     * Determines if a modified URL should be considered cross-origin with
+     * respect to an original URL.
+     */
+    public static function isCrossOrigin(UriInterface $original, UriInterface $modified) : bool
+    {
+        if (\strcasecmp($original->getHost(), $modified->getHost()) !== 0) {
+            return \true;
+        }
+        if ($original->getScheme() !== $modified->getScheme()) {
+            return \true;
+        }
+        if (self::computePort($original) !== self::computePort($modified)) {
+            return \true;
+        }
+        return \false;
+    }
+    private static function computePort(UriInterface $uri) : int
+    {
+        $port = $uri->getPort();
+        if (null !== $port) {
+            return $port;
+        }
+        return 'https' === $uri->getScheme() ? 443 : 80;
+    }
+    private function __construct()
+    {
+        // cannot be instantiated
+    }
+}