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

vendor/Aws3/Aws/AbstractConfigurationProvider.php

@@ -0,0 +1,133 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Promise;
+/**
+ * A configuration provider is a function that returns a promise that is
+ * fulfilled with a configuration object. This class provides base functionality
+ * usable by specific configuration provider implementations
+ */
+abstract class AbstractConfigurationProvider
+{
+    const ENV_PROFILE = 'AWS_PROFILE';
+    const ENV_CONFIG_FILE = 'AWS_CONFIG_FILE';
+    public static $cacheKey;
+    protected static $interfaceClass;
+    protected static $exceptionClass;
+    /**
+     * Wraps a config provider and saves provided configuration in an
+     * instance of Aws\CacheInterface. Forwards calls when no config found
+     * in cache and updates cache with the results.
+     *
+     * @param callable $provider Configuration provider function to wrap
+     * @param CacheInterface $cache Cache to store configuration
+     * @param string|null $cacheKey (optional) Cache key to use
+     *
+     * @return callable
+     */
+    public static function cache(callable $provider, CacheInterface $cache, $cacheKey = null)
+    {
+        $cacheKey = $cacheKey ?: static::$cacheKey;
+        return function () use($provider, $cache, $cacheKey) {
+            $found = $cache->get($cacheKey);
+            if ($found instanceof static::$interfaceClass) {
+                return Promise\Create::promiseFor($found);
+            }
+            return $provider()->then(function ($config) use($cache, $cacheKey) {
+                $cache->set($cacheKey, $config);
+                return $config;
+            });
+        };
+    }
+    /**
+     * Creates an aggregate configuration provider that invokes the provided
+     * variadic providers one after the other until a provider returns
+     * configuration.
+     *
+     * @return callable
+     */
+    public static function chain()
+    {
+        $links = \func_get_args();
+        if (empty($links)) {
+            throw new \InvalidArgumentException('No providers in chain');
+        }
+        return function () use($links) {
+            /** @var callable $parent */
+            $parent = \array_shift($links);
+            $promise = $parent();
+            while ($next = \array_shift($links)) {
+                $promise = $promise->otherwise($next);
+            }
+            return $promise;
+        };
+    }
+    /**
+     * Gets the environment's HOME directory if available.
+     *
+     * @return null|string
+     */
+    protected static function getHomeDir()
+    {
+        // On Linux/Unix-like systems, use the HOME environment variable
+        if ($homeDir = \getenv('HOME')) {
+            return $homeDir;
+        }
+        // Get the HOMEDRIVE and HOMEPATH values for Windows hosts
+        $homeDrive = \getenv('HOMEDRIVE');
+        $homePath = \getenv('HOMEPATH');
+        return $homeDrive && $homePath ? $homeDrive . $homePath : null;
+    }
+    /**
+     * Gets default config file location from environment, falling back to aws
+     * default location
+     *
+     * @return string
+     */
+    protected static function getDefaultConfigFilename()
+    {
+        if ($filename = \getenv(self::ENV_CONFIG_FILE)) {
+            return $filename;
+        }
+        return self::getHomeDir() . '/.aws/config';
+    }
+    /**
+     * Wraps a config provider and caches previously provided configuration.
+     *
+     * @param callable $provider Config provider function to wrap.
+     *
+     * @return callable
+     */
+    public static function memoize(callable $provider)
+    {
+        return function () use($provider) {
+            static $result;
+            static $isConstant;
+            // Constant config will be returned constantly.
+            if ($isConstant) {
+                return $result;
+            }
+            // Create the initial promise that will be used as the cached value
+            if (null === $result) {
+                $result = $provider();
+            }
+            // Return config and set flag that provider is already set
+            return $result->then(function ($config) use(&$isConstant) {
+                $isConstant = \true;
+                return $config;
+            });
+        };
+    }
+    /**
+     * Reject promise with standardized exception.
+     *
+     * @param $msg
+     * @return Promise\RejectedPromise
+     */
+    protected static function reject($msg)
+    {
+        $exceptionClass = static::$exceptionClass;
+        return new Promise\RejectedPromise(new $exceptionClass($msg));
+    }
+}