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/GuzzleHttp/TransferStats.php

@@ -0,0 +1,114 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\RequestInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\ResponseInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\UriInterface;
+/**
+ * Represents data at the point after it was transferred either successfully
+ * or after a network error.
+ */
+final class TransferStats
+{
+    /**
+     * @var RequestInterface
+     */
+    private $request;
+    /**
+     * @var ResponseInterface|null
+     */
+    private $response;
+    /**
+     * @var float|null
+     */
+    private $transferTime;
+    /**
+     * @var array
+     */
+    private $handlerStats;
+    /**
+     * @var mixed|null
+     */
+    private $handlerErrorData;
+    /**
+     * @param RequestInterface       $request          Request that was sent.
+     * @param ResponseInterface|null $response         Response received (if any)
+     * @param float|null             $transferTime     Total handler transfer time.
+     * @param mixed                  $handlerErrorData Handler error data.
+     * @param array                  $handlerStats     Handler specific stats.
+     */
+    public function __construct(RequestInterface $request, ?ResponseInterface $response = null, ?float $transferTime = null, $handlerErrorData = null, array $handlerStats = [])
+    {
+        $this->request = $request;
+        $this->response = $response;
+        $this->transferTime = $transferTime;
+        $this->handlerErrorData = $handlerErrorData;
+        $this->handlerStats = $handlerStats;
+    }
+    public function getRequest() : RequestInterface
+    {
+        return $this->request;
+    }
+    /**
+     * Returns the response that was received (if any).
+     */
+    public function getResponse() : ?ResponseInterface
+    {
+        return $this->response;
+    }
+    /**
+     * Returns true if a response was received.
+     */
+    public function hasResponse() : bool
+    {
+        return $this->response !== null;
+    }
+    /**
+     * Gets handler specific error data.
+     *
+     * This might be an exception, a integer representing an error code, or
+     * anything else. Relying on this value assumes that you know what handler
+     * you are using.
+     *
+     * @return mixed
+     */
+    public function getHandlerErrorData()
+    {
+        return $this->handlerErrorData;
+    }
+    /**
+     * Get the effective URI the request was sent to.
+     */
+    public function getEffectiveUri() : UriInterface
+    {
+        return $this->request->getUri();
+    }
+    /**
+     * Get the estimated time the request was being transferred by the handler.
+     *
+     * @return float|null Time in seconds.
+     */
+    public function getTransferTime() : ?float
+    {
+        return $this->transferTime;
+    }
+    /**
+     * Gets an array of all of the handler specific transfer data.
+     */
+    public function getHandlerStats() : array
+    {
+        return $this->handlerStats;
+    }
+    /**
+     * Get a specific handler statistic from the handler by name.
+     *
+     * @param string $stat Handler specific transfer stat to retrieve.
+     *
+     * @return mixed|null
+     */
+    public function getHandlerStat(string $stat)
+    {
+        return $this->handlerStats[$stat] ?? null;
+    }
+}