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/Crypto/AesGcmEncryptingStream.php

@@ -0,0 +1,94 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto\Polyfill\AesGcm;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto\Polyfill\Key;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Psr7\StreamDecoratorTrait;
+use DeliciousBrains\WP_Offload_Media\Aws3\Psr\Http\Message\StreamInterface;
+use RuntimeException;
+/**
+ * @internal Represents a stream of data to be gcm encrypted.
+ */
+class AesGcmEncryptingStream implements AesStreamInterface, AesStreamInterfaceV2
+{
+    use StreamDecoratorTrait;
+    private $aad;
+    private $initializationVector;
+    private $key;
+    private $keySize;
+    private $plaintext;
+    private $tag = '';
+    private $tagLength;
+    /**
+     * @var StreamInterface
+     */
+    private $stream;
+    /**
+     * Same as non-static 'getAesName' method, allowing calls in a static
+     * context.
+     *
+     * @return string
+     */
+    public static function getStaticAesName()
+    {
+        return 'AES/GCM/NoPadding';
+    }
+    /**
+     * @param StreamInterface $plaintext
+     * @param string $key
+     * @param string $initializationVector
+     * @param string $aad
+     * @param int $tagLength
+     * @param int $keySize
+     */
+    public function __construct(StreamInterface $plaintext, $key, $initializationVector, $aad = '', $tagLength = 16, $keySize = 256)
+    {
+        $this->plaintext = $plaintext;
+        $this->key = $key;
+        $this->initializationVector = $initializationVector;
+        $this->aad = $aad;
+        $this->tagLength = $tagLength;
+        $this->keySize = $keySize;
+        // unsetting the property forces the first access to go through
+        // __get().
+        unset($this->stream);
+    }
+    public function getOpenSslName()
+    {
+        return "aes-{$this->keySize}-gcm";
+    }
+    /**
+     * Same as static method and retained for backwards compatibility
+     *
+     * @return string
+     */
+    public function getAesName()
+    {
+        return self::getStaticAesName();
+    }
+    public function getCurrentIv()
+    {
+        return $this->initializationVector;
+    }
+    public function createStream()
+    {
+        if (\version_compare(\PHP_VERSION, '7.1', '<')) {
+            return Psr7\Utils::streamFor(AesGcm::encrypt((string) $this->plaintext, $this->initializationVector, new Key($this->key), $this->aad, $this->tag, $this->keySize));
+        } else {
+            return Psr7\Utils::streamFor(\openssl_encrypt((string) $this->plaintext, $this->getOpenSslName(), $this->key, \OPENSSL_RAW_DATA, $this->initializationVector, $this->tag, $this->aad, $this->tagLength));
+        }
+    }
+    /**
+     * @return string
+     */
+    public function getTag()
+    {
+        return $this->tag;
+    }
+    public function isWritable() : bool
+    {
+        return \false;
+    }
+}