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

classes/integrations/integration-manager.php

@@ -0,0 +1,94 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Integrations;
+
+class Integration_Manager {
+
+	/**
+	 * @var Integration_Manager
+	 */
+	protected static $instance;
+
+	/**
+	 * @var Integration[]
+	 */
+	private $integrations;
+
+	/**
+	 * Protected constructor to prevent creating a new instance of the
+	 * class via the `new` operator from outside this class.
+	 */
+	protected function __construct() {
+		$this->integrations = array();
+
+		add_action( 'as3cf_setup', array( $this, 'setup' ) );
+	}
+
+	/**
+	 * Make this class a singleton.
+	 *
+	 * Use this instead of __construct().
+	 *
+	 * @return Integration_Manager
+	 */
+	public static function get_instance() {
+		if ( ! isset( static::$instance ) && ! ( self::$instance instanceof Integration_Manager ) ) {
+			static::$instance = new Integration_Manager();
+		}
+
+		return static::$instance;
+	}
+
+	/**
+	 * Getter for integration class instance
+	 *
+	 * @param string $integration_key
+	 *
+	 * @return Integration|null
+	 */
+	public function get_integration( $integration_key ) {
+		if ( ! empty( $this->integrations[ $integration_key ] ) ) {
+			return $this->integrations[ $integration_key ];
+		}
+
+		return null;
+	}
+
+	/**
+	 * Register integration.
+	 *
+	 * @param string      $integration_key
+	 * @param Integration $integration
+	 */
+	public function register_integration( $integration_key, Integration $integration ) {
+		if ( $integration::is_installed() ) {
+			$integration->init();
+
+			$this->integrations[ $integration_key ] = $integration;
+		}
+	}
+
+	/**
+	 * Set up the registered integrations.
+	 *
+	 * @return void
+	 */
+	public function setup() {
+		foreach ( $this->integrations as $integration ) {
+			$integration->setup();
+		}
+	}
+
+	/**
+	 * As this class is a singleton it should not be clone-able.
+	 */
+	protected function __clone() {
+	}
+
+	/**
+	 * As this class is a singleton it should not be able to be unserialized.
+	 */
+	public function __wakeup() {
+	}
+
+}