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/Endpoint/EndpointProvider.php

@@ -0,0 +1,89 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Endpoint;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception\UnresolvedEndpointException;
+/**
+ * Endpoint providers.
+ *
+ * An endpoint provider is a function that accepts a hash of endpoint options,
+ * including but not limited to "service" and "region" key value pairs. The
+ * endpoint provider function returns a hash of endpoint data, which MUST
+ * include an "endpoint" key value pair that represents the resolved endpoint
+ * or NULL if an endpoint cannot be determined.
+ *
+ * You can wrap your calls to an endpoint provider with the
+ * {@see EndpointProvider::resolve} function to ensure that an endpoint hash is
+ * created. If an endpoint hash is not created, then the resolve() function
+ * will throw an {@see Aws\Exception\UnresolvedEndpointException}.
+ *
+ *     use Aws\Endpoint\EndpointProvider;
+ *     $provider = EndpointProvider::defaultProvider();
+ *     // Returns an array or NULL.
+ *     $endpoint = $provider(['service' => 'ec2', 'region' => 'us-west-2']);
+ *     // Returns an endpoint array or throws.
+ *     $endpoint = EndpointProvider::resolve($provider, [
+ *         'service' => 'ec2',
+ *         'region'  => 'us-west-2'
+ *     ]);
+ *
+ * You can compose multiple providers into a single provider using
+ * {@see Aws\or_chain}. This function accepts providers as arguments and
+ * returns a new function that will invoke each provider until a non-null value
+ * is returned.
+ *
+ *     $a = function (array $args) {
+ *         if ($args['region'] === 'my-test-region') {
+ *             return ['endpoint' => 'http://localhost:123/api'];
+ *         }
+ *     };
+ *     $b = EndpointProvider::defaultProvider();
+ *     $c = \Aws\or_chain($a, $b);
+ *     $config = ['service' => 'ec2', 'region' => 'my-test-region'];
+ *     $res = $c($config);  // $a handles this.
+ *     $config['region'] = 'us-west-2';
+ *     $res = $c($config); // $b handles this.
+ */
+class EndpointProvider
+{
+    /**
+     * Resolves and endpoint provider and ensures a non-null return value.
+     *
+     * @param callable $provider Provider function to invoke.
+     * @param array    $args     Endpoint arguments to pass to the provider.
+     *
+     * @return array
+     * @throws UnresolvedEndpointException
+     */
+    public static function resolve(callable $provider, array $args = [])
+    {
+        $result = $provider($args);
+        if (\is_array($result)) {
+            return $result;
+        }
+        throw new UnresolvedEndpointException('Unable to resolve an endpoint using the provider arguments: ' . \json_encode($args) . '. Note: you can provide an "endpoint" ' . 'option to a client constructor to bypass invoking an endpoint ' . 'provider.');
+    }
+    /**
+     * Creates and returns the default SDK endpoint provider.
+     *
+     * @deprecated Use an instance of \Aws\Endpoint\Partition instead.
+     *
+     * @return callable
+     */
+    public static function defaultProvider()
+    {
+        return PartitionEndpointProvider::defaultProvider();
+    }
+    /**
+     * Creates and returns an endpoint provider that uses patterns from an
+     * array.
+     *
+     * @param array $patterns Endpoint patterns
+     *
+     * @return callable
+     */
+    public static function patterns(array $patterns)
+    {
+        return new PatternEndpointProvider($patterns);
+    }
+}