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

interfaces/settings-interface.php

@@ -0,0 +1,164 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media;
+
+interface Settings_Interface {
+	/**
+	 * Returns keyed array of all settings values regardless of whether explicitly set or not.
+	 *
+	 * @param bool $pseudo Include pseudo settings that are derived rather than saved?
+	 *
+	 * @return array
+	 */
+	public function get_all_settings( bool $pseudo = true ): array;
+
+	/**
+	 * Get a specific setting.
+	 *
+	 * @param string $key
+	 * @param mixed  $default
+	 *
+	 * @return mixed
+	 */
+	public function get_setting( string $key, $default = '' );
+
+	/**
+	 * Get the plugin's settings array.
+	 *
+	 * @param bool $force
+	 *
+	 * @return array
+	 */
+	public function get_settings( bool $force = false ): array;
+
+	/**
+	 * Gets a single setting that has been defined in the plugin settings constant.
+	 *
+	 * @param string $key
+	 * @param mixed  $default
+	 *
+	 * @return mixed
+	 */
+	public function get_defined_setting( string $key, $default = '' );
+
+	/**
+	 * Get all settings that have been defined via constant for the plugin.
+	 *
+	 * @param bool $force
+	 *
+	 * @return array
+	 */
+	public function get_defined_settings( bool $force = false ): array;
+
+	/**
+	 * Set a setting.
+	 *
+	 * @param string $key
+	 * @param mixed  $value
+	 */
+	public function set_setting( string $key, $value );
+
+	/**
+	 * Bulk set the settings array.
+	 *
+	 * @param array $settings
+	 */
+	public function set_settings( array $settings );
+
+	/**
+	 * Save the settings to the database.
+	 */
+	public function save_settings();
+
+	/**
+	 * Delete a setting.
+	 *
+	 * @param string $key
+	 */
+	public function remove_setting( string $key );
+
+	/**
+	 * Ensure that sensitive settings are obfuscated.
+	 *
+	 * @param array $settings
+	 *
+	 * @return array
+	 */
+	public function obfuscate_sensitive_settings( array $settings ): array;
+
+	/**
+	 * Sanitize a setting value, maybe.
+	 *
+	 * @param string $key
+	 * @param mixed  $value
+	 *
+	 * @return array|bool|string
+	 */
+	public function sanitize_setting( string $key, $value );
+
+	/**
+	 * Allowed settings keys for this plugin.
+	 *
+	 * @param bool $include_legacy Should legacy keys be included? Optional, default false.
+	 *
+	 * @return array
+	 */
+	public function get_allowed_settings_keys( bool $include_legacy = false ): array;
+
+	/**
+	 * Get the settings that should not be shown once saved.
+	 *
+	 * @return array
+	 */
+	public function get_sensitive_settings(): array;
+
+	/**
+	 * Get the blacklisted settings for monitoring changes in defines.
+	 * These settings will not be saved in the database.
+	 *
+	 * @return array
+	 */
+	public function get_monitored_settings_blacklist(): array;
+
+	/**
+	 * List of settings that should skip full sanitize.
+	 *
+	 * @return array
+	 */
+	public function get_skip_sanitize_settings(): array;
+
+	/**
+	 * List of settings that should be treated as paths.
+	 *
+	 * @return array
+	 */
+	public function get_path_format_settings(): array;
+
+	/**
+	 * List of settings that should be treated as directory paths.
+	 *
+	 * @return array
+	 */
+	public function get_prefix_format_settings(): array;
+
+	/**
+	 * List of settings that should be treated as booleans.
+	 *
+	 * @return array
+	 */
+	public function get_boolean_format_settings(): array;
+
+	/**
+	 * Getter for $saving_settings.
+	 *
+	 * @return bool
+	 */
+	public function saving_settings(): bool;
+
+	/**
+	 * Setter for $saving_settings.
+	 *
+	 * @param bool $saving
+	 */
+	public function set_saving_settings( bool $saving );
+}