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/pro/as3cf-pro-installer.php

@@ -0,0 +1,155 @@
+<?php
+
+class AS3CF_Pro_Installer extends AS3CF_Compatibility_Check {
+
+	/**
+	 * @var array
+	 */
+	protected $required_plugins;
+
+	/**
+	 * @var AS3CF_Pro_Plugin_Installer
+	 */
+	protected $plugin_installer;
+
+	/**
+	 * AS3CF_Pro_Installer constructor.
+	 *
+	 * @param string $plugin_file_path
+	 */
+	public function __construct( $plugin_file_path ) {
+		parent::__construct(
+			'WP Offload Media',
+			'amazon-s3-and-cloudfront-pro',
+			$plugin_file_path
+		);
+
+		// Fire up the plugin installer
+		if ( is_admin() ) {
+			$this->plugin_installer = new AS3CF_Pro_Plugin_Installer( 'installer', $this->plugin_slug, $this->plugin_file_path );
+			$this->plugin_installer->set_plugins_to_install( $this->required_plugins_not_installed() );
+		}
+	}
+
+	/**
+	 * Are all the required plugins installed?
+	 *
+	 * @return bool
+	 */
+	public function is_setup() {
+		$plugins_not_installed = $this->required_plugins_not_installed();
+
+		return empty( $plugins_not_installed );
+	}
+
+	/**
+	 * Are all the required plugins activated?
+	 *
+	 * @return bool
+	 */
+	public function are_required_plugins_activated() {
+		$plugins_not_activated = $this->required_plugins_not_activated();
+
+		return empty( $plugins_not_activated );
+	}
+
+	/**
+	 * If the plugin is setup use the default compatible check
+	 *
+	 * @param bool $installed Check to see if the plugins are installed
+	 *
+	 * @return bool
+	 */
+	function is_compatible( $installed = true ) {
+		if ( $this->is_setup() || false === $installed ) {
+			return parent::is_compatible();
+		}
+
+		return false;
+	}
+
+	/**
+	 * The required plugins for this plugin
+	 *
+	 * @return array
+	 */
+	public function get_required_plugins() {
+		if ( is_null( $this->required_plugins ) ) {
+			$this->required_plugins = array();
+		}
+
+		return $this->required_plugins;
+	}
+
+	/**
+	 * Check if any of the required plugins are installed
+	 *
+	 * @return array
+	 */
+	public function required_plugins_not_installed() {
+		$plugins          = array();
+		$required_plugins = $this->get_required_plugins();
+
+		foreach ( $required_plugins as $slug => $plugin ) {
+			$filename = ( isset( $plugin['file'] ) ) ? $plugin['file'] : $slug;
+			if ( ! class_exists( $plugin['class'] ) && ! file_exists( WP_PLUGIN_DIR . '/' . $slug . '/' . $filename . '.php' ) ) {
+				$plugins[ $slug ] = $plugin['name'];
+			}
+		}
+
+		return $plugins;
+	}
+
+	/**
+	 * Check if any of the required plugins are activated
+	 *
+	 * @return array
+	 */
+	public function required_plugins_not_activated() {
+		$plugins          = array();
+		$required_plugins = $this->get_required_plugins();
+
+		foreach ( $required_plugins as $slug => $plugin ) {
+			if ( ! class_exists( $plugin['class'] ) ) {
+				$plugins[ $slug ] = $plugin['name'];
+			}
+		}
+
+		return $plugins;
+	}
+
+	/**
+	 * Generate the plugin info URL for thickbox
+	 *
+	 * @param string $slug
+	 *
+	 * @return string
+	 */
+	function get_plugin_info_url( $slug ) {
+		return self_admin_url( 'plugin-install.php?tab=plugin-information&amp;plugin=' . $slug . '&amp;TB_iframe=true&amp;width=600&amp;height=800' );
+	}
+
+	/**
+	 * Display a custom install notice if the plugin is not setup
+	 */
+	function get_admin_notice() {
+		$plugins_not_installed = $this->required_plugins_not_installed();
+		if ( empty( $plugins_not_installed ) ) {
+			parent::get_admin_notice();
+
+			return;
+		}
+
+		$this->plugin_installer->load_installer_assets();
+
+		if ( $notices = get_site_transient( 'as3cfpro_installer_notices' ) ) {
+			if ( isset( $notices['filesystem_error'] ) ) {
+				// Don't show the installer notice if we have filesystem credential issues
+				return;
+			}
+		}
+
+		$install_notice = untrailingslashit( plugin_dir_path( $this->plugin_file_path ) ) . '/view/pro/install-notice.php';
+		include $install_notice;
+	}
+}