feat(docker-watcher): phase 11 - frontend embed & SSE

Embed SvelteKit static build in Go binary via go:embed. Event bus
for pub/sub with deploy log, instance status, and deploy status events.
SSE endpoints for real-time streaming. Frontend SSE client with
exponential backoff reconnection. Makefile for build pipeline.
Update Phase 12 auth plan with OAuth2/OIDC support.

web/src/routes/+layout.svelte

@@ -1,8 +1,11 @@
 <script lang="ts">
 	import '../app.css';
 	import type { Snippet } from 'svelte';
+	import { onMount, onDestroy } from 'svelte';
 	import { page } from '$app/stores';
 	import Toast from '$lib/components/Toast.svelte';
+	import { connectGlobalEvents, type SSEConnection } from '$lib/sse';
+	import { instanceStatusStore } from '$lib/stores/instance-status';
 
 	interface Props {
 		children: Snippet;
@@ -21,6 +24,24 @@
 		if (href === '/') return pathname === '/';
 		return pathname.startsWith(href);
 	}
+
+	let sseConnection: SSEConnection | null = null;
+
+	onMount(() => {
+		sseConnection = connectGlobalEvents({
+			onInstanceStatus(payload) {
+				instanceStatusStore.update(payload);
+			},
+			onDeployStatus(payload) {
+				instanceStatusStore.notifyDeploy(payload);
+			}
+		});
+	});
+
+	onDestroy(() => {
+		sseConnection?.close();
+		sseConnection = null;
+	});
 </script>
 
 <div class="flex h-screen bg-gray-50">