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/EndpointParameterMiddleware.php

@@ -0,0 +1,69 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Api\Service;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\RequestInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Log\InvalidArgumentException;
+/**
+ * Used to update the host based on a modeled endpoint trait
+ *
+ * IMPORTANT: this middleware must be added after the "build" step.
+ *
+ * @internal
+ */
+class EndpointParameterMiddleware
+{
+    /** @var callable */
+    private $nextHandler;
+    /** @var Service */
+    private $service;
+    /**
+     * Create a middleware wrapper function
+     *
+     * @param Service $service
+     * @param array $args
+     * @return \Closure
+     */
+    public static function wrap(Service $service)
+    {
+        return function (callable $handler) use($service) {
+            return new self($handler, $service);
+        };
+    }
+    public function __construct(callable $nextHandler, Service $service)
+    {
+        $this->nextHandler = $nextHandler;
+        $this->service = $service;
+    }
+    public function __invoke(CommandInterface $command, RequestInterface $request)
+    {
+        $nextHandler = $this->nextHandler;
+        $operation = $this->service->getOperation($command->getName());
+        if (!empty($operation['endpoint']['hostPrefix'])) {
+            $prefix = $operation['endpoint']['hostPrefix'];
+            // Captures endpoint parameters stored in the modeled host.
+            // These are denoted by enclosure in braces, i.e. '{param}'
+            \preg_match_all("/\\{([a-zA-Z0-9]+)}/", $prefix, $parameters);
+            if (!empty($parameters[1])) {
+                // Captured parameters without braces stored in $parameters[1],
+                // which should correspond to members in the Command object
+                foreach ($parameters[1] as $index => $parameter) {
+                    if (empty($command[$parameter])) {
+                        throw new \InvalidArgumentException("The parameter '{$parameter}' must be set and not empty.");
+                    }
+                    // Captured parameters with braces stored in $parameters[0],
+                    // which are replaced by their corresponding Command value
+                    $prefix = \str_replace($parameters[0][$index], $command[$parameter], $prefix);
+                }
+            }
+            $uri = $request->getUri();
+            $host = $prefix . $uri->getHost();
+            if (!\DeliciousBrains\WP_Offload_Media\Aws3\Aws\is_valid_hostname($host)) {
+                throw new \InvalidArgumentException("The supplied parameters result in an invalid hostname: '{$host}'.");
+            }
+            $request = $request->withUri($uri->withHost($host));
+        }
+        return $nextHandler($command, $request);
+    }
+}