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/CheckAgain.svelte

@@ -0,0 +1,66 @@
+<script>
+	import Button from "./Button.svelte";
+	import {
+		api,
+		revalidatingSettings,
+		settings_validation,
+		state,
+		strings
+	} from "../js/stores";
+	import {delayMin} from "../js/delay";
+
+	export let section = "";
+
+	$: refreshing = $revalidatingSettings;
+
+	let datetime = new Date( $settings_validation[ section ].timestamp * 1000 ).toString();
+
+	/**
+	 * Calls the API to revalidate settings.
+	 */
+	async function revalidate() {
+		let start = Date.now();
+		let params = {
+			revalidateSettings: true,
+			section: section,
+		};
+
+		refreshing = true;
+		let json = await api.get( "state", params );
+		await delayMin( start, 1000 );
+		state.updateState( json );
+		refreshing = false;
+	}
+</script>
+
+<div class="check-again">
+	{#if !refreshing}
+		<Button refresh {refreshing} title={$strings.check_again_desc} on:click={revalidate}>
+			{$strings.check_again_title}
+		</Button>
+	{:else}
+		<Button refresh {refreshing} title={$strings.check_again_desc}>
+			{$strings.check_again_active}
+		</Button>
+	{/if}
+	<span class="last-update" title="{datetime}">
+		{$settings_validation[ section ].last_update}
+	</span>
+</div>
+
+<style>
+	div.check-again {
+		display: flex;
+		flex-direction: column;
+		align-items: flex-end;
+		white-space: nowrap;
+		min-width: 6rem;
+		padding-left: 0.5rem;
+		color: var(--as3cf-color-gray-700);
+	}
+
+	#as3cf-settings .check-again .last-update {
+		padding-right: 2px;
+		margin-top: 2px;
+	}
+</style>