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/Gcp/google/gax/src/Options/OptionsTrait.php

@@ -0,0 +1,84 @@
+<?php
+
+/*
+ * Copyright 2023 Google LLC
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+namespace DeliciousBrains\WP_Offload_Media\Gcp\Google\ApiCore\Options;
+
+use DeliciousBrains\WP_Offload_Media\Gcp\Google\ApiCore\ValidationException;
+use BadMethodCallException;
+/**
+ * Trait implemented by any class representing an associative array of PHP options.
+ * This provides validation and typehinting to loosely typed associative arrays.
+ */
+trait OptionsTrait
+{
+    /**
+     * @param string $filePath
+     * @throws ValidationException
+     */
+    private static function validateFileExists(string $filePath)
+    {
+        if (!\file_exists($filePath)) {
+            throw new ValidationException("Could not find specified file: {$filePath}");
+        }
+    }
+    public function offsetExists($offset) : bool
+    {
+        return isset($this->{$offset});
+    }
+    #[\ReturnTypeWillChange]
+    public function offsetGet($offset)
+    {
+        return $this->{$offset};
+    }
+    /**
+     * @throws BadMethodCallException
+     */
+    public function offsetSet($offset, $value) : void
+    {
+        throw new BadMethodCallException('Cannot set options through array access. Use the setters instead');
+    }
+    /**
+     * @throws BadMethodCallException
+     */
+    public function offsetUnset($offset) : void
+    {
+        throw new BadMethodCallException('Cannot unset options through array access. Use the setters instead');
+    }
+    public function toArray() : array
+    {
+        $arr = [];
+        foreach (\get_object_vars($this) as $key => $value) {
+            $arr[$key] = $value;
+        }
+        return $arr;
+    }
+}