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/Retry/RetryHelperTrait.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Retry;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception\AwsException;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\ResultInterface;
+trait RetryHelperTrait
+{
+    private function addRetryHeader($request, $retries, $delayBy)
+    {
+        return $request->withHeader('aws-sdk-retry', "{$retries}/{$delayBy}");
+    }
+    private function updateStats($retries, $delay, array &$stats)
+    {
+        if (!isset($stats['total_retry_delay'])) {
+            $stats['total_retry_delay'] = 0;
+        }
+        $stats['total_retry_delay'] += $delay;
+        $stats['retries_attempted'] = $retries;
+    }
+    private function updateHttpStats($value, array &$stats)
+    {
+        if (empty($stats['http'])) {
+            $stats['http'] = [];
+        }
+        if ($value instanceof AwsException) {
+            $resultStats = $value->getTransferInfo();
+            $stats['http'][] = $resultStats;
+        } elseif ($value instanceof ResultInterface) {
+            $resultStats = isset($value['@metadata']['transferStats']['http'][0]) ? $value['@metadata']['transferStats']['http'][0] : [];
+            $stats['http'][] = $resultStats;
+        }
+    }
+    private function bindStatsToReturn($return, array $stats)
+    {
+        if ($return instanceof ResultInterface) {
+            if (!isset($return['@metadata'])) {
+                $return['@metadata'] = [];
+            }
+            $return['@metadata']['transferStats'] = $stats;
+        } elseif ($return instanceof AwsException) {
+            $return->setTransferInfo($stats);
+        }
+        return $return;
+    }
+}