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/Credentials/Credentials.php

@@ -0,0 +1,105 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Credentials;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Identity\AwsCredentialIdentity;
+/**
+ * Basic implementation of the AWS Credentials interface that allows callers to
+ * pass in the AWS Access Key and AWS Secret Access Key in the constructor.
+ */
+class Credentials extends AwsCredentialIdentity implements CredentialsInterface, \Serializable
+{
+    private $key;
+    private $secret;
+    private $token;
+    private $expires;
+    private $accountId;
+    /**
+     * Constructs a new BasicAWSCredentials object, with the specified AWS
+     * access key and AWS secret key
+     *
+     * @param string $key     AWS access key ID
+     * @param string $secret  AWS secret access key
+     * @param string $token   Security token to use
+     * @param int    $expires UNIX timestamp for when credentials expire
+     */
+    public function __construct($key, $secret, $token = null, $expires = null, $accountId = null)
+    {
+        $this->key = \trim((string) $key);
+        $this->secret = \trim((string) $secret);
+        $this->token = $token;
+        $this->expires = $expires;
+        $this->accountId = $accountId;
+    }
+    public static function __set_state(array $state)
+    {
+        return new self($state['key'], $state['secret'], $state['token'], $state['expires'], $state['accountId']);
+    }
+    public function getAccessKeyId()
+    {
+        return $this->key;
+    }
+    public function getSecretKey()
+    {
+        return $this->secret;
+    }
+    public function getSecurityToken()
+    {
+        return $this->token;
+    }
+    public function getExpiration()
+    {
+        return $this->expires;
+    }
+    public function isExpired()
+    {
+        return $this->expires !== null && \time() >= $this->expires;
+    }
+    public function getAccountId()
+    {
+        return $this->accountId;
+    }
+    public function toArray()
+    {
+        return ['key' => $this->key, 'secret' => $this->secret, 'token' => $this->token, 'expires' => $this->expires, 'accountId' => $this->accountId];
+    }
+    public function serialize()
+    {
+        return \json_encode($this->__serialize());
+    }
+    public function unserialize($serialized)
+    {
+        $data = \json_decode($serialized, \true);
+        $this->__unserialize($data);
+    }
+    public function __serialize()
+    {
+        return $this->toArray();
+    }
+    public function __unserialize($data)
+    {
+        $this->key = $data['key'];
+        $this->secret = $data['secret'];
+        $this->token = $data['token'];
+        $this->expires = $data['expires'];
+        $this->accountId = $data['accountId'];
+    }
+    /**
+     * Internal-only. Used when IMDS is unreachable
+     * or returns expires credentials.
+     *
+     * @internal
+     */
+    public function extendExpiration()
+    {
+        $extension = \mt_rand(5, 10);
+        $this->expires = \time() + $extension * 60;
+        $message = <<<EOT
+Attempting credential expiration extension due to a credential service 
+availability issue. A refresh of these credentials will be attempted again 
+after {$extension} minutes.
+
+EOT;
+        \trigger_error($message, \E_USER_WARNING);
+    }
+}