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/SupportForm.svelte

@@ -0,0 +1,139 @@
+<script>
+	import {diagnostics, notifications, strings} from "../js/stores";
+	import {licence} from "./stores";
+	import Button from "../components/Button.svelte";
+
+	let email = "";
+	let subject = "";
+	let message = "";
+	let includeDiagnostics = true;
+
+	/**
+	 * Potentially returns a reason that the Submit button is disabled.
+	 *
+	 * @param {string} email
+	 * @param {string} subject
+	 * @param {string} message
+	 *
+	 * @return {string}
+	 */
+	function getDisabledReason( email, subject, message ) {
+		let reason = "";
+
+		if ( !email || !subject || !message ) {
+			reason = "Email, Subject and Message required.";
+		}
+
+		return reason;
+	}
+
+	$: disabledReason = getDisabledReason( email, subject, message );
+
+	/**
+	 * Handles a Submit button click.
+	 *
+	 * @param {Object} event
+	 *
+	 * @return {Promise<void>}
+	 */
+	async function submitSupportRequest( event ) {
+		const formData = new FormData();
+
+		formData.append( "email", email );
+		formData.append( "subject", subject );
+		formData.append( "message", message );
+
+		if ( includeDiagnostics ) {
+			formData.append( "local-diagnostic", "1" );
+			formData.append( "local-diagnostic-content", $diagnostics );
+		}
+
+		let response;
+
+		try {
+			response = await fetch(
+				$licence.support_url,
+				{
+					method: "POST",
+					body: formData
+				}
+			);
+		} catch ( error ) {
+			const notice = $strings.send_email_post_error + error.message;
+
+			notifications.add( {
+				id: "support-send-email-response",
+				type: "error",
+				dismissible: true,
+				only_show_on_tab: "support",
+				message: notice
+			} );
+
+			return;
+		}
+
+		const json = await response.json();
+
+		if ( json.hasOwnProperty( "errors" ) ) {
+			for ( const [key, value] of Object.entries( json.errors ) ) {
+				const notice = $strings.send_email_api_error + value;
+
+				notifications.add( {
+					id: "support-send-email-response",
+					type: "error",
+					dismissible: true,
+					only_show_on_tab: "support",
+					message: notice
+				} );
+			}
+
+			return;
+		}
+
+		if ( json.hasOwnProperty( "success" ) && json.success === 1 ) {
+			notifications.add( {
+				id: "support-send-email-response",
+				type: "success",
+				dismissible: true,
+				only_show_on_tab: "support",
+				message: $strings.send_email_success
+			} );
+
+			email = "";
+			subject = "";
+			message = "";
+			includeDiagnostics = true;
+
+			return;
+		}
+
+		notifications.add( {
+			id: "support-send-email-response",
+			type: "error",
+			dismissible: true,
+			only_show_on_tab: "support",
+			message: $strings.send_email_unexpected_error
+		} );
+	}
+</script>
+
+<label for="email" class="input-label">From</label>
+<select name="email" id="email" bind:value={email}>
+	{#each $licence.support_email_addresses as supportEmail}
+		<option value={supportEmail}>{supportEmail}</option>
+	{/each}
+	<option value="">{$strings.select_email}</option>
+</select>
+<p class="note">{@html $strings.email_note}</p>
+<input type="text" id="subject" name="subject" bind:value={subject} minlength="4" placeholder={$strings.email_subject_placeholder}>
+<textarea id="message" name="message" bind:value={message} rows="8" placeholder={$strings.email_message_placeholder}></textarea>
+<div class="actions">
+	<div class="checkbox">
+		<label for="include-diagnostics">
+			<input type="checkbox" id="include-diagnostics" name="include-diagnostics" bind:checked={includeDiagnostics}>{$strings.attach_diagnostics}
+		</label>
+	</div>
+	<Button primary on:click={submitSupportRequest} disabled={disabledReason} title={disabledReason}>{$strings.send_email}</Button>
+</div>
+<p class="note first">{$strings.having_trouble}</p>
+<p class="note">{@html $strings.email_instead}</p>