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/Auth/AuthSchemeResolver.php

@@ -0,0 +1,134 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Auth;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Auth\Exception\UnresolvedAuthSchemeException;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Identity\AwsCredentialIdentity;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Identity\BearerTokenIdentity;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Promise\PromiseInterface;
+/**
+ * Houses logic for selecting an auth scheme modeled in a service's `auth` trait.
+ * The `auth` trait can be modeled either in a service's metadata, or at the operation level.
+ */
+class AuthSchemeResolver implements AuthSchemeResolverInterface
+{
+    const UNSIGNED_BODY = '-unsigned-body';
+    /**
+     * @var string[] Default mapping of modeled auth trait auth schemes
+     *               to the SDK's supported signature versions.
+     */
+    private static $defaultAuthSchemeMap = ['aws.auth#sigv4' => 'v4', 'aws.auth#sigv4a' => 'v4a', 'smithy.api#httpBearerAuth' => 'bearer', 'smithy.api#noAuth' => 'anonymous'];
+    /**
+     * @var array Mapping of auth schemes to signature versions used in
+     *            resolving a signature version.
+     */
+    private $authSchemeMap;
+    private $tokenProvider;
+    private $credentialProvider;
+    public function __construct(callable $credentialProvider, callable $tokenProvider = null, array $authSchemeMap = [])
+    {
+        $this->credentialProvider = $credentialProvider;
+        $this->tokenProvider = $tokenProvider;
+        $this->authSchemeMap = empty($authSchemeMap) ? self::$defaultAuthSchemeMap : $authSchemeMap;
+    }
+    /**
+     * Accepts a priority-ordered list of auth schemes and an Identity
+     * and selects the first compatible auth schemes, returning a normalized
+     * signature version.  For example, based on the default auth scheme mapping,
+     * if `aws.auth#sigv4` is selected, `v4` will be returned.
+     *
+     * @param array $authSchemes
+     * @param $identity
+     *
+     * @return string
+     * @throws UnresolvedAuthSchemeException
+     */
+    public function selectAuthScheme(array $authSchemes, array $args = []) : string
+    {
+        $failureReasons = [];
+        foreach ($authSchemes as $authScheme) {
+            $normalizedAuthScheme = $this->authSchemeMap[$authScheme] ?? $authScheme;
+            if ($this->isCompatibleAuthScheme($normalizedAuthScheme)) {
+                if ($normalizedAuthScheme === 'v4' && !empty($args['unsigned_payload'])) {
+                    return $normalizedAuthScheme . self::UNSIGNED_BODY;
+                }
+                return $normalizedAuthScheme;
+            } else {
+                $failureReasons[] = $this->getIncompatibilityMessage($normalizedAuthScheme);
+            }
+        }
+        throw new UnresolvedAuthSchemeException('Could not resolve an authentication scheme: ' . \implode('; ', $failureReasons));
+    }
+    /**
+     * Determines compatibility based on either Identity or the availability
+     * of the CRT extension.
+     *
+     * @param $authScheme
+     *
+     * @return bool
+     */
+    private function isCompatibleAuthScheme($authScheme) : bool
+    {
+        switch ($authScheme) {
+            case 'v4':
+            case 'anonymous':
+                return $this->hasAwsCredentialIdentity();
+            case 'v4a':
+                return \extension_loaded('awscrt') && $this->hasAwsCredentialIdentity();
+            case 'bearer':
+                return $this->hasBearerTokenIdentity();
+            default:
+                return \false;
+        }
+    }
+    /**
+     * Provides incompatibility messages in the event an incompatible auth scheme
+     * is encountered.
+     *
+     * @param $authScheme
+     *
+     * @return string
+     */
+    private function getIncompatibilityMessage($authScheme) : string
+    {
+        switch ($authScheme) {
+            case 'v4':
+                return 'Signature V4 requires AWS credentials for request signing';
+            case 'anonymous':
+                return 'Anonymous signatures require AWS credentials for request signing';
+            case 'v4a':
+                return 'The aws-crt-php extension and AWS credentials are required to use Signature V4A';
+            case 'bearer':
+                return 'Bearer token credentials must be provided to use Bearer authentication';
+            default:
+                return "The service does not support `{$authScheme}` authentication.";
+        }
+    }
+    /**
+     * @return bool
+     */
+    private function hasAwsCredentialIdentity() : bool
+    {
+        $fn = $this->credentialProvider;
+        $result = $fn();
+        if ($result instanceof PromiseInterface) {
+            return $result->wait() instanceof AwsCredentialIdentity;
+        }
+        return $result instanceof AwsCredentialIdentity;
+    }
+    /**
+     * @return bool
+     */
+    private function hasBearerTokenIdentity() : bool
+    {
+        if ($this->tokenProvider) {
+            $fn = $this->tokenProvider;
+            $result = $fn();
+            if ($result instanceof PromiseInterface) {
+                return $result->wait() instanceof BearerTokenIdentity;
+            }
+            return $result instanceof BearerTokenIdentity;
+        }
+        return \false;
+    }
+}

vendor/Aws3/Aws/Auth/AuthSchemeResolverInterface.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Auth;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Identity\IdentityInterface;
+/**
+ * An AuthSchemeResolver object determines which auth scheme will be used for request signing.
+ */
+interface AuthSchemeResolverInterface
+{
+    /**
+     * Selects an auth scheme for request signing.
+     *
+     * @param array $authSchemes a priority-ordered list of authentication schemes.
+     * @param IdentityInterface $identity Credentials to be used in request signing.
+     *
+     * @return string
+     */
+    public function selectAuthScheme(array $authSchemes, array $args) : ?string;
+}

vendor/Aws3/Aws/Auth/AuthSelectionMiddleware.php

@@ -0,0 +1,78 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Auth;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Api\Service;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\CommandInterface;
+use Closure;
+use DeliciousBrains\WP_Offload_Media\Aws3\GuzzleHttp\Promise\Promise;
+/**
+ * Handles auth scheme resolution. If a service models and auth scheme using
+ * the `auth` trait and the operation or metadata levels, this middleware will
+ * attempt to select the first compatible auth scheme it encounters and apply its
+ * signature version to the command's `@context` property bag.
+ *
+ * IMPORTANT: this middleware must be added to the "build" step.
+ *
+ * @internal
+ */
+class AuthSelectionMiddleware
+{
+    /** @var callable */
+    private $nextHandler;
+    /** @var AuthSchemeResolverInterface */
+    private $authResolver;
+    /** @var Service */
+    private $api;
+    /**
+     * Create a middleware wrapper function
+     *
+     * @param AuthSchemeResolverInterface $authResolver
+     * @param Service $api
+     * @return Closure
+     */
+    public static function wrap(AuthSchemeResolverInterface $authResolver, Service $api) : Closure
+    {
+        return function (callable $handler) use($authResolver, $api) {
+            return new self($handler, $authResolver, $api);
+        };
+    }
+    /**
+     * @param callable $nextHandler
+     * @param $authResolver
+     * @param callable $identityProvider
+     * @param Service $api
+     */
+    public function __construct(callable $nextHandler, AuthSchemeResolverInterface $authResolver, Service $api)
+    {
+        $this->nextHandler = $nextHandler;
+        $this->authResolver = $authResolver;
+        $this->api = $api;
+    }
+    /**
+     * @param CommandInterface $command
+     *
+     * @return Promise
+     */
+    public function __invoke(CommandInterface $command)
+    {
+        $nextHandler = $this->nextHandler;
+        $serviceAuth = $this->api->getMetadata('auth') ?: [];
+        $operation = $this->api->getOperation($command->getName());
+        $operationAuth = $operation['auth'] ?? [];
+        $unsignedPayload = $operation['unsignedpayload'] ?? \false;
+        $resolvableAuth = $operationAuth ?: $serviceAuth;
+        if (!empty($resolvableAuth)) {
+            if (isset($command['@context']['auth_scheme_resolver']) && $command['@context']['auth_scheme_resolver'] instanceof AuthSchemeResolverInterface) {
+                $resolver = $command['@context']['auth_scheme_resolver'];
+            } else {
+                $resolver = $this->authResolver;
+            }
+            $selectedAuthScheme = $resolver->selectAuthScheme($resolvableAuth, ['unsigned_payload' => $unsignedPayload]);
+            if (!empty($selectedAuthScheme)) {
+                $command['@context']['signature_version'] = $selectedAuthScheme;
+            }
+        }
+        return $nextHandler($command);
+    }
+}

vendor/Aws3/Aws/Auth/Exception/UnresolvedAuthSchemeException.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Auth\Exception;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\HasMonitoringEventsTrait;
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\MonitoringEventsInterface;
+/**
+ * Represents an error when attempting to resolve authentication.
+ */
+class UnresolvedAuthSchemeException extends \RuntimeException implements MonitoringEventsInterface
+{
+    use HasMonitoringEventsTrait;
+}