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/pro/UpdateObjectACLsPromptSubPage.svelte

@@ -0,0 +1,62 @@
+<script>
+	import {createEventDispatcher, getContext, hasContext} from "svelte";
+	import {writable} from "svelte/store";
+	import {pop} from "svelte-spa-router";
+	import {strings} from "../js/stores";
+	import {tools} from "./stores";
+	import SubPage from "../components/SubPage.svelte";
+	import Panel from "../components/Panel.svelte";
+	import PanelRow from "../components/PanelRow.svelte";
+	import BackNextButtonsRow from "../components/BackNextButtonsRow.svelte";
+
+	const tool = $tools.update_acls;
+	const dispatch = createEventDispatcher();
+
+	// Parent page may want to be locked.
+	let settingsLocked = writable( false );
+
+	if ( hasContext( "settingsLocked" ) ) {
+		settingsLocked = getContext( "settingsLocked" );
+	}
+
+	/**
+	 * Handles a Skip button click.
+	 *
+	 * @return {Promise<void>}
+	 */
+	async function handleSkip() {
+		dispatch( "routeEvent", { event: "next", default: "/" } );
+	}
+
+	/**
+	 * Handles a Next button click.
+	 *
+	 * @return {Promise<void>}
+	 */
+	async function handleNext() {
+		await tools.start( tool );
+		dispatch( "routeEvent", { event: "next", default: "/" } );
+	}
+</script>
+
+<SubPage name="update-acls" route="/storage/update-acls">
+	<Panel
+		heading={tool.title}
+		helpURL={tool.doc_url}
+		helpDesc={tool.doc_desc}
+		multi
+	>
+		<PanelRow class="body flex-column">
+			<p>{@html tool.prompt}</p>
+		</PanelRow>
+	</Panel>
+
+	<BackNextButtonsRow
+		on:skip={handleSkip}
+		on:next={handleNext}
+		skipText={$strings.no}
+		nextText={$strings.yes}
+		skipVisible={true}
+		nextDisabled={$settingsLocked}
+	/>
+</SubPage>