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/Gcp/psr/http-message/CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+All notable changes to this project will be documented in this file, in reverse chronological order by release.
+
+## 1.0.1 - 2016-08-06
+
+### Added
+
+- Nothing.
+
+### Deprecated
+
+- Nothing.
+
+### Removed
+
+- Nothing.
+
+### Fixed
+
+- Updated all `@return self` annotation references in interfaces to use
+  `@return static`, which more closelly follows the semantics of the
+  specification.
+- Updated the `MessageInterface::getHeaders()` return annotation to use the
+  value `string[][]`, indicating the format is a nested array of strings.
+- Updated the `@link` annotation for `RequestInterface::withRequestTarget()`
+  to point to the correct section of RFC 7230.
+- Updated the `ServerRequestInterface::withUploadedFiles()` parameter annotation
+  to add the parameter name (`$uploadedFiles`).
+- Updated a `@throws` annotation for the `UploadedFileInterface::moveTo()`
+  method to correctly reference the method parameter (it was referencing an
+  incorrect parameter name previously).
+
+## 1.0.0 - 2016-05-18
+
+Initial stable release; reflects accepted PSR-7 specification.