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/Exception/MultipartUploadException.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\HasMonitoringEventsTrait;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\MonitoringEventsInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Multipart\UploadState;
+class MultipartUploadException extends \RuntimeException implements MonitoringEventsInterface
+{
+    use HasMonitoringEventsTrait;
+    /** @var UploadState State of the erroneous transfer */
+    private $state;
+    /**
+     * @param UploadState      $state Upload state at time of the exception.
+     * @param \Exception|array $prev  Exception being thrown.
+     */
+    public function __construct(UploadState $state, $prev = null)
+    {
+        $msg = 'An exception occurred while performing a multipart upload';
+        if (\is_array($prev)) {
+            $msg = \strtr($msg, ['performing' => 'uploading parts to']);
+            $msg .= ". The following parts had errors:\n";
+            /** @var $error AwsException */
+            foreach ($prev as $part => $error) {
+                $msg .= "- Part {$part}: " . $error->getMessage() . "\n";
+            }
+        } elseif ($prev instanceof AwsException) {
+            switch ($prev->getCommand()->getName()) {
+                case 'CreateMultipartUpload':
+                case 'InitiateMultipartUpload':
+                    $action = 'initiating';
+                    break;
+                case 'CompleteMultipartUpload':
+                    $action = 'completing';
+                    break;
+            }
+            if (isset($action)) {
+                $msg = \strtr($msg, ['performing' => $action]);
+            }
+            $msg .= ": {$prev->getMessage()}";
+        }
+        if (!$prev instanceof \Exception) {
+            $prev = null;
+        }
+        parent::__construct($msg, 0, $prev);
+        $this->state = $state;
+    }
+    /**
+     * Get the state of the transfer
+     *
+     * @return UploadState
+     */
+    public function getState()
+    {
+        return $this->state;
+    }
+}