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

ui/components/Page.svelte

@@ -0,0 +1,33 @@
+<script>
+	import {onMount, createEventDispatcher, setContext} from "svelte";
+	import {location} from "svelte-spa-router";
+	import {current_settings} from "../js/stores";
+
+	export let name = "";
+
+	// In some scenarios a Page should have some SubPage behaviours.
+	export let subpage = false;
+
+	export let initialSettings = $current_settings;
+
+	const dispatch = createEventDispatcher();
+
+	// When a page is created, store a copy of the initial settings
+	// so they can be compared with any changes later.
+	setContext( "initialSettings", initialSettings );
+
+	// Tell the route event handlers about the initial settings too.
+	onMount( () => {
+		dispatch( "routeEvent", {
+			event: "page.initial.settings",
+			data: {
+				settings: initialSettings,
+				location: $location
+			}
+		} );
+	} );
+</script>
+
+<div class="page-wrapper {name}" class:subpage>
+	<slot/>
+</div>