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/ToolNotification.svelte

@@ -0,0 +1,76 @@
+<script>
+	import {fade, slide} from "svelte/transition";
+	import {api, strings} from "../js/stores";
+	import Notification from "../components/Notification.svelte";
+
+	export let notification;
+
+	let expanded = true;
+
+	/**
+	 * Handles Dismiss All Errors for item click.
+	 *
+	 * @param {string} tool_key
+	 * @param {Object} item
+	 *
+	 * @return {Promise<void>}
+	 */
+	async function dismissAll( tool_key, item ) {
+		await api.delete( "tools", {
+			id: tool_key,
+			blog_id: item.blog_id,
+			source_type: item.source_type,
+			source_id: item.source_id
+		} );
+	}
+
+	/**
+	 * Handles Dismiss Individual Error for item click.
+	 *
+	 * @param {string} tool_key
+	 * @param {Object} item
+	 * @param {number} index
+	 *
+	 * @return {Promise<void>}
+	 */
+	async function dismissError( tool_key, item, index ) {
+		await api.delete( "tools", {
+			id: tool_key,
+			blog_id: item.blog_id,
+			source_type: item.source_type,
+			source_id: item.source_id,
+			errors: index
+		} );
+	}
+</script>
+
+{#if notification.hasOwnProperty( "class" ) && notification.class === "tool-error" && notification.hasOwnProperty( "errors" )}
+	<Notification notification={notification} expandable bind:expanded>
+		<svelte:fragment slot="details">
+			{#if expanded}
+				<div class="details" transition:slide>
+					{#each notification.errors.details as item, index}
+						<div class="item" transition:fade>
+							<div class="summary">
+								<div class="title">
+									{(index + 1) + ". " + item.source_type_name}
+									<a href={item.edit_url.url}>#{item.source_id}</a>
+								</div>
+								<button class="dismiss" on:click|preventDefault={() => dismissAll(notification.errors.tool_key, item)}>{$strings.dismiss}</button>
+							</div>
+							<ul class="detail">
+								{#each item.messages as message, index}
+									<li>{@html message}</li>
+								{/each}
+							</ul>
+						</div>
+					{/each}
+				</div>
+			{/if}
+		</svelte:fragment>
+	</Notification>
+{:else}
+	<Notification notification={notification}>
+		<slot/>
+	</Notification>
+{/if}