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/Promise/RejectionException.php

@@ -0,0 +1,41 @@
+<?php
+
+declare (strict_types=1);
+namespace DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Promise;
+
+/**
+ * A special exception that is thrown when waiting on a rejected promise.
+ *
+ * The reason value is available via the getReason() method.
+ */
+class RejectionException extends \RuntimeException
+{
+    /** @var mixed Rejection reason. */
+    private $reason;
+    /**
+     * @param mixed       $reason      Rejection reason.
+     * @param string|null $description Optional description.
+     */
+    public function __construct($reason, ?string $description = null)
+    {
+        $this->reason = $reason;
+        $message = 'The promise was rejected';
+        if ($description) {
+            $message .= ' with reason: ' . $description;
+        } elseif (\is_string($reason) || \is_object($reason) && \method_exists($reason, '__toString')) {
+            $message .= ' with reason: ' . $this->reason;
+        } elseif ($reason instanceof \JsonSerializable) {
+            $message .= ' with reason: ' . \json_encode($this->reason, \JSON_PRETTY_PRINT);
+        }
+        parent::__construct($message);
+    }
+    /**
+     * Returns the rejection reason.
+     *
+     * @return mixed
+     */
+    public function getReason()
+    {
+        return $this->reason;
+    }
+}