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/CipherBuilderTrait.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto\Cipher;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception\CryptoException;
+trait CipherBuilderTrait
+{
+    /**
+     * Returns an identifier recognizable by `openssl_*` functions, such as
+     * `aes-256-cbc` or `aes-128-ctr`.
+     *
+     * @param string $cipherName Name of the cipher being used for encrypting
+     *                           or decrypting.
+     * @param int $keySize Size of the encryption key, in bits, that will be
+     *                     used.
+     *
+     * @return string
+     */
+    protected function getCipherOpenSslName($cipherName, $keySize)
+    {
+        return "aes-{$keySize}-{$cipherName}";
+    }
+    /**
+     * Constructs a CipherMethod for the given name, initialized with the other
+     * data passed for use in encrypting or decrypting.
+     *
+     * @param string $cipherName Name of the cipher to generate for encrypting.
+     * @param string $iv Base Initialization Vector for the cipher.
+     * @param int $keySize Size of the encryption key, in bits, that will be
+     *                     used.
+     *
+     * @return CipherMethod
+     *
+     * @internal
+     */
+    protected function buildCipherMethod($cipherName, $iv, $keySize)
+    {
+        switch ($cipherName) {
+            case 'cbc':
+                return new Cbc($iv, $keySize);
+            default:
+                return null;
+        }
+    }
+    /**
+     * Performs a reverse lookup to get the openssl_* cipher name from the
+     * AESName passed in from the MetadataEnvelope.
+     *
+     * @param $aesName
+     *
+     * @return string
+     *
+     * @internal
+     */
+    protected function getCipherFromAesName($aesName)
+    {
+        switch ($aesName) {
+            case 'AES/GCM/NoPadding':
+                return 'gcm';
+            case 'AES/CBC/PKCS5Padding':
+                return 'cbc';
+            default:
+                throw new CryptoException('Unrecognized or unsupported' . ' AESName for reverse lookup.');
+        }
+    }
+}