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/S3/BucketEndpointMiddleware.php

@@ -0,0 +1,102 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\S3;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\CommandInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\RequestInterface;
+/**
+ * Used to update the host used for S3 requests in the case of using a
+ * "bucket endpoint" or CNAME bucket.
+ *
+ * IMPORTANT: this middleware must be added after the "build" step.
+ *
+ * @internal
+ */
+class BucketEndpointMiddleware
+{
+    private static $exclusions = ['GetBucketLocation' => \true];
+    private $nextHandler;
+    /**
+     * Create a middleware wrapper function.
+     *
+     * @return callable
+     */
+    public static function wrap()
+    {
+        return function (callable $handler) {
+            return new self($handler);
+        };
+    }
+    public function __construct(callable $nextHandler)
+    {
+        $this->nextHandler = $nextHandler;
+    }
+    public function __invoke(CommandInterface $command, RequestInterface $request)
+    {
+        $nextHandler = $this->nextHandler;
+        $bucket = $command['Bucket'];
+        if ($bucket && !isset(self::$exclusions[$command->getName()])) {
+            $request = $this->modifyRequest($request, $command);
+        }
+        return $nextHandler($command, $request);
+    }
+    /**
+     * Performs a one-time removal of Bucket from path, then if
+     * the bucket name is duplicated in the path, performs additional
+     * removal which is dependent on the number of occurrences of the bucket
+     * name in a path-like format in the key name.
+     *
+     * @return string
+     */
+    private function removeBucketFromPath($path, $bucket, $key)
+    {
+        $occurrencesInKey = $this->getBucketNameOccurrencesInKey($key, $bucket);
+        do {
+            $len = \strlen($bucket) + 1;
+            if (\substr($path, 0, $len) === "/{$bucket}") {
+                $path = \substr($path, $len);
+            }
+        } while (\substr_count($path, "/{$bucket}") > $occurrencesInKey + 1);
+        return $path ?: '/';
+    }
+    private function removeDuplicateBucketFromHost($host, $bucket)
+    {
+        if (\substr_count($host, $bucket) > 1) {
+            while (\strpos($host, "{$bucket}.{$bucket}") === 0) {
+                $hostArr = \explode('.', $host);
+                \array_shift($hostArr);
+                $host = \implode('.', $hostArr);
+            }
+        }
+        return $host;
+    }
+    private function getBucketNameOccurrencesInKey($key, $bucket)
+    {
+        $occurrences = 0;
+        if (empty($key)) {
+            return $occurrences;
+        }
+        $segments = \explode('/', $key);
+        foreach ($segments as $segment) {
+            if (\strpos($segment, $bucket) === 0) {
+                $occurrences++;
+            }
+        }
+        return $occurrences;
+    }
+    private function modifyRequest(RequestInterface $request, CommandInterface $command)
+    {
+        $key = isset($command['Key']) ? $command['Key'] : null;
+        $uri = $request->getUri();
+        $path = $uri->getPath();
+        $host = $uri->getHost();
+        $bucket = $command['Bucket'];
+        $path = $this->removeBucketFromPath($path, $bucket, $key);
+        $host = $this->removeDuplicateBucketFromHost($host, $bucket);
+        // Modify the Key to make sure the key is encoded, but slashes are not.
+        if ($key) {
+            $path = S3Client::encodeKey(\rawurldecode($path));
+        }
+        return $request->withUri($uri->withHost($host)->withPath($path));
+    }
+}