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/ProgressBar.svelte

@@ -0,0 +1,52 @@
+<script>
+	import {cubicOut} from "svelte/easing";
+	import {tweened} from "svelte/motion";
+
+	export let percentComplete = 0;
+	export let starting = false;
+	export let running = false;
+	export let paused = false;
+	export let title = "";
+
+	let progressTweened = tweened( 0, {
+		duration: 400,
+		easing: cubicOut
+	} );
+
+	/**
+	 * Utility function for reactively getting the progress.
+	 *
+	 * @param {number} percent
+	 *
+	 * @return {number|*}
+	 */
+	function getProgress( percent ) {
+		if ( percent < 1 ) {
+			return 0;
+		}
+
+		if ( percent >= 100 ) {
+			return 100;
+		}
+
+		return percent;
+	}
+
+	$: progressTweened.set( getProgress( percentComplete ) );
+	$: complete = percentComplete >= 100;
+</script>
+
+<!-- TODO: Fix a11y. -->
+<!-- svelte-ignore a11y-no-static-element-interactions -->
+<!-- svelte-ignore a11y-click-events-have-key-events -->
+<div
+	class="progress-bar"
+	class:stripe={running && ! paused}
+	class:animate={starting}
+	{title}
+	on:click|preventDefault
+	on:mouseenter
+	on:mouseleave
+>
+	<span class="indicator animate" class:complete class:running style="width: {$progressTweened}%"></span>
+</div>