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/EndpointV2/EndpointV2SerializerTrait.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\EndpointV2;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Api\Serializer\RestSerializer;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\EndpointV2\Ruleset\RulesetEndpoint;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7\Uri;
+/**
+ * Set of helper functions used to set endpoints and endpoint
+ * properties derived from dynamic endpoint resolution.
+ *
+ * @internal
+ */
+trait EndpointV2SerializerTrait
+{
+    /**
+     * Applies a resolved endpoint, headers and any custom HTTP schemes provided
+     * in client configuration to options which are applied to the serialized request.
+     *
+     * @param $endpoint
+     * @param $headers
+     *
+     * @return void
+     */
+    private function setEndpointV2RequestOptions(RulesetEndpoint $endpoint, array &$headers) : void
+    {
+        $this->applyHeaders($endpoint, $headers);
+        $resolvedUrl = $endpoint->getUrl();
+        $this->applyScheme($resolvedUrl);
+        $this->endpoint = $this instanceof RestSerializer ? new Uri($resolvedUrl) : $resolvedUrl;
+    }
+    /**
+     * Combines modeled headers and headers resolved from an endpoint object.
+     *
+     * @param $endpoint
+     * @param $headers
+     * @return void
+     */
+    private function applyHeaders(RulesetEndpoint $endpoint, array &$headers) : void
+    {
+        if (!\is_null($endpoint->getHeaders())) {
+            $headers = \array_merge($headers, $endpoint->getHeaders());
+        }
+    }
+    /**
+     * Applies custom HTTP schemes provided in client configuration.
+     *
+     * @param $resolvedUrl
+     * @return void
+     */
+    private function applyScheme(&$resolvedUrl) : void
+    {
+        $resolvedEndpointScheme = \parse_url($resolvedUrl, \PHP_URL_SCHEME);
+        $scheme = $this->endpoint instanceof Uri ? $this->endpoint->getScheme() : \parse_url($this->endpoint, \PHP_URL_SCHEME);
+        if (!empty($scheme) && $scheme !== $resolvedEndpointScheme) {
+            $resolvedUrl = \str_replace($resolvedEndpointScheme, $scheme, $resolvedUrl);
+        }
+    }
+}