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/Polyfill/NeedsTrait.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace DeliciousBrains\WP_Offload_Media\Aws3\Aws\Crypto\Polyfill;
+
+use DeliciousBrains\WP_Offload_Media\Aws3\Aws\Exception\CryptoPolyfillException;
+/**
+ * Trait NeedsTrait
+ */
+trait NeedsTrait
+{
+    /**
+     * Preconditions, postconditions, and loop invariants are very
+     * useful for safe programing.  They also document the specifications.
+     * This function is to help simplify the semantic burden of parsing
+     * these constructions.
+     *
+     * Instead of constructions like
+     *     if (!(GOOD CONDITION)) {
+     *         throw new \Exception('condition not true');
+     *     }
+     *
+     * you can write:
+     *     needs(GOOD CONDITION, 'condition not true');
+     * @param $condition
+     * @param $errorMessage
+     * @param null $exceptionClass
+     */
+    public static function needs($condition, $errorMessage, $exceptionClass = null)
+    {
+        if (!$condition) {
+            if (!$exceptionClass) {
+                $exceptionClass = CryptoPolyfillException::class;
+            }
+            throw new $exceptionClass($errorMessage);
+        }
+    }
+}