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/Cipher/Cbc.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto\Cipher;
+
+use InvalidArgumentException;
+use LogicException;
+/**
+ * An implementation of the CBC cipher for use with an AesEncryptingStream or
+ * AesDecrypting stream.
+ *
+ * This cipher method is deprecated and in maintenance mode - no new updates will be
+ * released. Please see https://docs.aws.amazon.com/general/latest/gr/aws_sdk_cryptography.html
+ * for more information.
+ *
+ * @deprecated
+ */
+class Cbc implements CipherMethod
+{
+    const BLOCK_SIZE = 16;
+    /**
+     * @var string
+     */
+    private $baseIv;
+    /**
+     * @var string
+     */
+    private $iv;
+    /**
+     * @var int
+     */
+    private $keySize;
+    /**
+     * @param string $iv Base Initialization Vector for the cipher.
+     * @param int $keySize Size of the encryption key, in bits, that will be
+     *                     used.
+     *
+     * @throws InvalidArgumentException Thrown if the passed iv does not match
+     *                                  the iv length required by the cipher.
+     */
+    public function __construct($iv, $keySize = 256)
+    {
+        $this->baseIv = $this->iv = $iv;
+        $this->keySize = $keySize;
+        if (\strlen($iv) !== \openssl_cipher_iv_length($this->getOpenSslName())) {
+            throw new InvalidArgumentException('Invalid initialization vector');
+        }
+    }
+    public function getOpenSslName()
+    {
+        return "aes-{$this->keySize}-cbc";
+    }
+    public function getAesName()
+    {
+        return 'AES/CBC/PKCS5Padding';
+    }
+    public function getCurrentIv()
+    {
+        return $this->iv;
+    }
+    public function requiresPadding()
+    {
+        return \true;
+    }
+    public function seek($offset, $whence = \SEEK_SET)
+    {
+        if ($offset === 0 && $whence === \SEEK_SET) {
+            $this->iv = $this->baseIv;
+        } else {
+            throw new LogicException('CBC initialization only support being' . ' rewound, not arbitrary seeking.');
+        }
+    }
+    public function update($cipherTextBlock)
+    {
+        $this->iv = \substr($cipherTextBlock, self::BLOCK_SIZE * -1);
+    }
+}