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/TaskQueue.php

@@ -0,0 +1,65 @@
+<?php
+
+declare (strict_types=1);
+namespace DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Promise;
+
+/**
+ * A task queue that executes tasks in a FIFO order.
+ *
+ * This task queue class is used to settle promises asynchronously and
+ * maintains a constant stack size. You can use the task queue asynchronously
+ * by calling the `run()` function of the global task queue in an event loop.
+ *
+ *     GuzzleHttp\Promise\Utils::queue()->run();
+ *
+ * @final
+ */
+class TaskQueue implements TaskQueueInterface
+{
+    private $enableShutdown = \true;
+    private $queue = [];
+    public function __construct(bool $withShutdown = \true)
+    {
+        if ($withShutdown) {
+            \register_shutdown_function(function () : void {
+                if ($this->enableShutdown) {
+                    // Only run the tasks if an E_ERROR didn't occur.
+                    $err = \error_get_last();
+                    if (!$err || $err['type'] ^ \E_ERROR) {
+                        $this->run();
+                    }
+                }
+            });
+        }
+    }
+    public function isEmpty() : bool
+    {
+        return !$this->queue;
+    }
+    public function add(callable $task) : void
+    {
+        $this->queue[] = $task;
+    }
+    public function run() : void
+    {
+        while ($task = \array_shift($this->queue)) {
+            /** @var callable $task */
+            $task();
+        }
+    }
+    /**
+     * The task queue will be run and exhausted by default when the process
+     * exits IFF the exit is not the result of a PHP E_ERROR error.
+     *
+     * You can disable running the automatic shutdown of the queue by calling
+     * this function. If you disable the task queue shutdown process, then you
+     * MUST either run the task queue (as a result of running your event loop
+     * or manually using the run() method) or wait on each outstanding promise.
+     *
+     * Note: This shutdown will occur before any destructors are triggered.
+     */
+    public function disableShutdown() : void
+    {
+        $this->enableShutdown = \false;
+    }
+}