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/OffloadStatus.svelte

@@ -0,0 +1,120 @@
+<script>
+	import {counts, strings, urls} from "../js/stores";
+	import {numToString} from "../js/numToString";
+	import ProgressBar from "../components/ProgressBar.svelte";
+	import OffloadStatusFlyout from "./OffloadStatusFlyout.svelte";
+
+	// Controls whether flyout is visible or not.
+	export let expanded = false;
+	export let flyoutButton = {};
+	export let hasFocus = false;
+
+	/**
+	 * Returns the numeric percentage progress for total offloaded media.
+	 *
+	 * @param {number} total
+	 * @param {number} offloaded
+	 *
+	 * @return {number}
+	 */
+	function getPercentComplete( total, offloaded ) {
+		if ( total < 1 || offloaded < 1 ) {
+			return 0;
+		}
+
+		const percent = Math.floor( Math.abs( offloaded / total * 100 ) );
+
+		if ( percent > 100 ) {
+			return 100;
+		}
+
+		return percent;
+	}
+
+	$: percentComplete = getPercentComplete( $counts.total, $counts.offloaded );
+	$: complete = percentComplete >= 100;
+
+	/**
+	 * Returns a formatted title string reflecting the current status.
+	 *
+	 * @param {number} percent
+	 * @param {number} total
+	 * @param {number} offloaded
+	 * @param {string} description
+	 *
+	 * @return {string}
+	 */
+	function getTitle( percent, total, offloaded, description ) {
+		return percent + "% (" + numToString( offloaded ) + "/" + numToString( total ) + ") " + description;
+	}
+
+	$: title = getTitle( percentComplete, $counts.total, $counts.offloaded, $strings.offloaded );
+
+	/**
+	 * Handles a click to toggle the flyout.
+	 */
+	function handleClick() {
+		expanded = !expanded;
+		flyoutButton.focus();
+
+		// We've handled the click.
+		return true;
+	}
+
+	/**
+	 * Keep track of when a child control gets mouse focus.
+	 */
+	function handleMouseEnter() {
+		hasFocus = true;
+	}
+
+	/**
+	 * Keep track of when a child control loses mouse focus.
+	 */
+	function handleMouseLeave() {
+		hasFocus = false;
+	}
+</script>
+
+<!-- TODO: Fix a11y. -->
+<!-- svelte-ignore a11y-no-static-element-interactions -->
+<div class="nav-status-wrapper" class:complete>
+	<!-- TODO: Fix a11y. -->
+	<!-- svelte-ignore a11y-click-events-have-key-events -->
+	<div
+		class="nav-status"
+		{title}
+		on:click|preventDefault={handleClick}
+		on:mouseenter={handleMouseEnter}
+		on:mouseleave={handleMouseLeave}
+	>
+		{#if complete}
+			<img
+				class="icon type"
+				src={$urls.assets + "img/icon/licence-checked.svg"}
+				alt="{title}"
+				{title}
+			/>
+		{/if}
+		<p
+			class="status-text"
+			{title}
+		>
+			<strong>{percentComplete}%</strong>
+			<span> {@html $strings.offloaded}</span>
+		</p>
+		<ProgressBar
+			{percentComplete}
+			{title}
+		/>
+	</div>
+	<slot name="flyout">
+		<OffloadStatusFlyout bind:expanded bind:hasFocus bind:buttonRef={flyoutButton}/>
+	</slot>
+</div>
+
+<style>
+	.nav-status-wrapper {
+		position: relative;
+	}
+</style>