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/psr/http-factory/src/ServerRequestFactoryInterface.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Gcp\Psr\Http\Message;
+
+interface ServerRequestFactoryInterface
+{
+    /**
+     * Create a new server request.
+     *
+     * Note that server-params are taken precisely as given - no parsing/processing
+     * of the given values is performed, and, in particular, no attempt is made to
+     * determine the HTTP method or URI, which must be provided explicitly.
+     *
+     * @param string $method The HTTP method associated with the request.
+     * @param UriInterface|string $uri The URI associated with the request. If
+     *     the value is a string, the factory MUST create a UriInterface
+     *     instance based on it.
+     * @param array $serverParams Array of SAPI parameters with which to seed
+     *     the generated request instance.
+     *
+     * @return ServerRequestInterface
+     */
+    public function createServerRequest(string $method, $uri, array $serverParams = []) : ServerRequestInterface;
+}