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/background-processes/add-metadata-process.php

@@ -0,0 +1,95 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Pro\Background_Processes;
+
+use DeliciousBrains\WP_Offload_Media\Items\Item;
+use DeliciousBrains\WP_Offload_Media\Items\Media_Library_Item;
+use Exception;
+
+class Add_Metadata_Process extends Uploader_Process {
+
+	/**
+	 * @var string
+	 */
+	protected $action = 'add_metadata';
+
+	/**
+	 * Increased batch limit as there is no network or file handling.
+	 *
+	 * @var int
+	 */
+	protected $limit = 2000;
+
+	/**
+	 * Increased chunk size as there is no network or file handling.
+	 *
+	 * @var int
+	 */
+	protected $chunk = 100;
+
+	/**
+	 * Create metadata as if item has been offloaded to provider, but don't actually do an offload.
+	 *
+	 * @param string $source_type
+	 * @param int    $source_id
+	 * @param int    $blog_id
+	 *
+	 * @return bool
+	 * @throws Exception
+	 */
+	protected function handle_item( $source_type, $source_id, $blog_id ) {
+		// Skip item if already on provider.
+		if ( Media_Library_Item::get_by_source_id( $source_id ) ) {
+			return false;
+		}
+
+		$options    = array(
+			'originator'            => Item::ORIGINATORS['metadata-tool'],
+			'is_verified'           => false,
+			'use_object_versioning' => false,
+		);
+		$as3cf_item = Media_Library_Item::create_from_source_id( $source_id, $options );
+
+		// Build error message
+		if ( is_wp_error( $as3cf_item ) ) {
+			foreach ( $as3cf_item->get_error_messages() as $error_message ) {
+				$error_msg = sprintf( __( 'Error adding metadata - %s', 'amazon-s3-and-cloudfront' ), $error_message );
+				$this->record_error( $blog_id, $source_type, $source_id, $error_msg );
+			}
+
+			return false;
+		} else {
+			$as3cf_item->save();
+		}
+
+		return true;
+	}
+
+	/**
+	 * Get reached license limit notice message.
+	 *
+	 * @return string
+	 */
+	protected function get_reached_license_limit_message() {
+		$account_link = sprintf( '<a href="%s" target="_blank">%s</a>', $this->as3cf->get_my_account_url(), __( 'My Account', 'amazon-s3-and-cloudfront' ) );
+		$notice_msg   = __( "You've reached your license limit so we've had to stop adding metadata. To add metadata to the rest of your Media Library, please upgrade your license from %s and simply start the add metadata tool again. It will start from where it stopped.", 'amazon-s3-and-cloudfront' );
+
+		return sprintf( $notice_msg, $account_link );
+	}
+
+	/**
+	 * Get complete notice message.
+	 *
+	 * @return string
+	 */
+	protected function get_complete_message() {
+		return __( 'Finished adding metadata to Media Library.', 'amazon-s3-and-cloudfront' );
+	}
+
+	/**
+	 * Called when background process has completed.
+	 */
+	protected function completed() {
+		$this->as3cf->update_media_library_total();
+	}
+}