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/upgrades/upgrade-content-replace-urls.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Upgrades;
+
+use AS3CF_Utils;
+
+/**
+ * Upgrade_Content_Replace_URLs Class
+ *
+ * This class handles replacing all S3 URLs in post
+ * content with the local URL.
+ *
+ * @since 1.2
+ */
+class Upgrade_Content_Replace_URLs extends Upgrade_Filter_Post {
+
+	/**
+	 * @var int
+	 */
+	protected $upgrade_id = 4;
+
+	/**
+	 * @var string
+	 */
+	protected $upgrade_name = 'replace_provider_urls';
+
+	/**
+	 * @var string
+	 */
+	protected $column_name = 'post_content';
+
+	/**
+	 * Get running update text.
+	 *
+	 * @return string
+	 */
+	protected function get_running_update_text() {
+		return __( 'and ensuring that only the local URL exists in post content.', 'amazon-s3-and-cloudfront' );
+	}
+
+	/**
+	 * Get running message.
+	 *
+	 * @return string
+	 */
+	protected function get_running_message() {
+		return sprintf( __( '<strong>Running Content Upgrade%1$s</strong><br>A find &amp; replace is running in the background to update URLs in your post content. %2$s', 'amazon-s3-and-cloudfront' ), $this->get_progress_text(), $this->get_generic_message() );
+	}
+
+	/**
+	 * Switch to a new blog for processing.
+	 *
+	 * @return bool
+	 */
+	protected function upgrade_blog() {
+		$this->upgrade_theme_mods();
+
+		return parent::upgrade_blog();
+	}
+
+	/**
+	 * Upgrade theme mods. Ensures background and header images have local URLs saved to the database.
+	 */
+	protected function upgrade_theme_mods() {
+		global $wpdb;
+
+		$mods = $wpdb->get_results( "SELECT * FROM `{$wpdb->options}` WHERE option_name LIKE 'theme_mods_%'" );
+
+		foreach ( $mods as $mod ) {
+			$value = AS3CF_Utils::maybe_unserialize( $mod->option_value );
+
+			if ( isset( $value['background_image'] ) ) {
+				$value['background_image'] = $this->as3cf->filter_provider->filter_customizer_image( $value['background_image'] );
+			}
+
+			if ( isset( $value['header_image'] ) ) {
+				$value['header_image'] = $this->as3cf->filter_provider->filter_customizer_image( $value['header_image'] );
+			}
+
+			if ( isset( $value['header_image_data'] ) ) {
+				$value['header_image_data'] = $this->as3cf->filter_provider->filter_header_image_data( $value['header_image_data'] );
+			}
+
+			$value = maybe_serialize( $value );
+
+			if ( $value !== $mod->option_value ) {
+				$wpdb->query( "UPDATE `{$wpdb->options}` SET option_value = '{$value}' WHERE option_id = '{$mod->option_id}'" );
+			}
+		}
+	}
+
+}