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/Api/Parser/Crc32ValidatingParser.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Api\Parser;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Api\StructureShape;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\CommandInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception\AwsException;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\ResponseInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\StreamInterface;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7;
+/**
+ * @internal Decorates a parser and validates the x-amz-crc32 header.
+ */
+class Crc32ValidatingParser extends AbstractParser
+{
+    /**
+     * @param callable $parser Parser to wrap.
+     */
+    public function __construct(callable $parser)
+    {
+        $this->parser = $parser;
+    }
+    public function __invoke(CommandInterface $command, ResponseInterface $response)
+    {
+        if ($expected = $response->getHeaderLine('x-amz-crc32')) {
+            $hash = \hexdec(Psr7\Utils::hash($response->getBody(), 'crc32b'));
+            if ($expected != $hash) {
+                throw new AwsException("crc32 mismatch. Expected {$expected}, found {$hash}.", $command, ['code' => 'ClientChecksumMismatch', 'connection_error' => \true, 'response' => $response]);
+            }
+        }
+        $fn = $this->parser;
+        return $fn($command, $response);
+    }
+    public function parseMemberFromStream(StreamInterface $stream, StructureShape $member, $response)
+    {
+        return $this->parser->parseMemberFromStream($stream, $member, $response);
+    }
+}