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/Psr7/Rfc7230.php

@@ -0,0 +1,22 @@
+<?php
+
+declare (strict_types=1);
+namespace DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7;
+
+/**
+ * @internal
+ */
+final class Rfc7230
+{
+    /**
+     * Header related regular expressions (based on amphp/http package)
+     *
+     * Note: header delimiter (\r\n) is modified to \r?\n to accept line feed only delimiters for BC reasons.
+     *
+     * @see https://github.com/amphp/http/blob/v1.0.1/src/Rfc7230.php#L12-L15
+     *
+     * @license https://github.com/amphp/http/blob/v1.0.1/LICENSE
+     */
+    public const HEADER_REGEX = "(^([^()<>@,;:\\\"/[\\]?={}\x01- ]++):[ \t]*+((?:[ \t]*+[!-~\x80-\xff]++)*+)[ \t]*+\r?\n)m";
+    public const HEADER_FOLD_REGEX = "(\r?\n[ \t]++)";
+}