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/Nav.svelte

@@ -0,0 +1,20 @@
+<script>
+	import {pages} from "../js/routes";
+	import NavItem from "./NavItem.svelte";
+	import OffloadStatus from "./OffloadStatus.svelte";
+</script>
+
+<div class="nav">
+	<div class="items">
+		<ul class="nav">
+			{#each $pages as tab (tab.position)}
+				{#if tab.nav && tab.title}
+					<NavItem {tab}/>
+				{/if}
+			{/each}
+		</ul>
+		<slot>
+			<OffloadStatus/>
+		</slot>
+	</div>
+</div>