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/RequestCompressionMiddleware.php

@@ -0,0 +1,116 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\RequestInterface;
+/**
+ * Used to compress request payloads if the service/operation support it.
+ *
+ * IMPORTANT: this middleware must be added after the "build" step.
+ *
+ * @internal
+ */
+class RequestCompressionMiddleware
+{
+    private $api;
+    private $minimumCompressionSize;
+    private $nextHandler;
+    private $encodings;
+    private $encoding;
+    private $encodingMap = ['gzip' => 'gzencode'];
+    /**
+     * Create a middleware wrapper function.
+     *
+     * @return callable
+     */
+    public static function wrap(array $config)
+    {
+        return function (callable $handler) use($config) {
+            return new self($handler, $config);
+        };
+    }
+    public function __construct(callable $nextHandler, $config)
+    {
+        $this->minimumCompressionSize = $this->determineMinimumCompressionSize($config);
+        $this->api = $config['api'];
+        $this->nextHandler = $nextHandler;
+    }
+    public function __invoke(CommandInterface $command, RequestInterface $request)
+    {
+        if (isset($command['@request_min_compression_size_bytes']) && \is_int($command['@request_min_compression_size_bytes']) && $this->isValidCompressionSize($command['@request_min_compression_size_bytes'])) {
+            $this->minimumCompressionSize = $command['@request_min_compression_size_bytes'];
+        }
+        $nextHandler = $this->nextHandler;
+        $operation = $this->api->getOperation($command->getName());
+        $compressionInfo = isset($operation['requestcompression']) ? $operation['requestcompression'] : null;
+        if (!$this->shouldCompressRequestBody($compressionInfo, $command, $operation, $request)) {
+            return $nextHandler($command, $request);
+        }
+        $this->encodings = $compressionInfo['encodings'];
+        $request = $this->compressRequestBody($request);
+        return $nextHandler($command, $request);
+    }
+    private function compressRequestBody(RequestInterface $request)
+    {
+        $fn = $this->determineEncoding();
+        if (\is_null($fn)) {
+            return $request;
+        }
+        $body = $request->getBody()->getContents();
+        $compressedBody = $fn($body);
+        return $request->withBody(Psr7\Utils::streamFor($compressedBody))->withHeader('content-encoding', $this->encoding);
+    }
+    private function determineEncoding()
+    {
+        foreach ($this->encodings as $encoding) {
+            if (isset($this->encodingMap[$encoding])) {
+                $this->encoding = $encoding;
+                return $this->encodingMap[$encoding];
+            }
+        }
+        return null;
+    }
+    private function shouldCompressRequestBody($compressionInfo, $command, $operation, $request)
+    {
+        if ($compressionInfo) {
+            if (isset($command['@disable_request_compression']) && $command['@disable_request_compression'] === \true) {
+                return \false;
+            } elseif ($this->hasStreamingTraitWithoutRequiresLength($command, $operation)) {
+                return \true;
+            }
+            $requestBodySize = $request->hasHeader('content-length') ? (int) $request->getHeaderLine('content-length') : $request->getBody()->getSize();
+            if ($requestBodySize >= $this->minimumCompressionSize) {
+                return \true;
+            }
+        }
+        return \false;
+    }
+    private function hasStreamingTraitWithoutRequiresLength($command, $operation)
+    {
+        foreach ($operation->getInput()->getMembers() as $name => $member) {
+            if (isset($command[$name]) && !empty($member['streaming']) && empty($member['requiresLength'])) {
+                return \true;
+            }
+        }
+        return \false;
+    }
+    private function determineMinimumCompressionSize($config)
+    {
+        if (\is_callable($config['request_min_compression_size_bytes'])) {
+            $minCompressionSz = $config['request_min_compression_size_bytes']();
+        } else {
+            $minCompressionSz = $config['request_min_compression_size_bytes'];
+        }
+        if ($this->isValidCompressionSize($minCompressionSz)) {
+            return $minCompressionSz;
+        }
+    }
+    private function isValidCompressionSize($compressionSize)
+    {
+        if (\is_numeric($compressionSize) && ($compressionSize >= 0 && $compressionSize <= 10485760)) {
+            return \true;
+        }
+        throw new \InvalidArgumentException('The minimum request compression size must be a ' . 'non-negative integer value between 0 and 10485760 bytes, inclusive.');
+    }
+}