feat: docker-compose stacks with Forge-themed UI

Adds a new Stacks feature: upload/edit docker-compose YAML,
deploy as atomic units, browse revisions, roll back, and
stream logs. Backend in internal/stack + internal/api/stacks.go,
persistent storage in internal/store/stacks.go.

Stacks pages (list, new, detail) use a modern Forge aesthetic —
Instrument Serif display type, JetBrains Mono for meta/code,
indigo ember accents, dot-grid hero, registration marks on
hover, terminal panel for logs. Palette is sourced from the
app's existing design tokens so the feature remains consistent
with the rest of Tinyforge.

Fonts self-hosted via @fontsource/instrument-serif and
@fontsource/jetbrains-mono to satisfy the strict CSP.

web/src/routes/+layout.svelte

@@ -6,7 +6,7 @@
 	import Toast from '$lib/components/Toast.svelte';
 	import ThemeToggle from '$lib/components/ThemeToggle.svelte';
 	import LocaleSwitcher from '$lib/components/LocaleSwitcher.svelte';
-	import { IconDashboard, IconProjects, IconDeploy, IconEvents, IconWifi, IconSettings, IconMenu, IconX, IconLogout, IconGlobe } from '$lib/components/icons';
+	import { IconDashboard, IconProjects, IconDeploy, IconEvents, IconWifi, IconSettings, IconMenu, IconX, IconLogout, IconGlobe, IconBox } from '$lib/components/icons';
 	import { goto } from '$app/navigation';
 	import { resolvedTheme, applyTheme } from '$lib/stores/theme';
 	import { exchangeOidcToken, setAuthToken, clearAuth, isAuthenticated } from '$lib/auth';
@@ -24,6 +24,7 @@
 		{ href: '/', labelKey: 'nav.dashboard', icon: 'dashboard' },
 		{ href: '/projects', labelKey: 'nav.projects', icon: 'projects' },
 		{ href: '/sites', labelKey: 'nav.sites', icon: 'globe' },
+		{ href: '/stacks', labelKey: 'nav.stacks', icon: 'stacks' },
 		{ href: '/deploy', labelKey: 'nav.deploy', icon: 'deploy' },
 		{ href: '/proxies', labelKey: 'nav.proxies', icon: 'proxies' },
 		{ href: '/events', labelKey: 'nav.events', icon: 'events' },
@@ -163,6 +164,8 @@
 						<IconProjects size={18} class="{active ? 'text-[var(--color-brand-600)]' : 'text-[var(--text-tertiary)] group-hover:text-[var(--text-secondary)]'} transition-colors duration-150" />
 					{:else if item.icon === 'globe'}
 						<IconGlobe size={18} class="{active ? 'text-[var(--color-brand-600)]' : 'text-[var(--text-tertiary)] group-hover:text-[var(--text-secondary)]'} transition-colors duration-150" />
+					{:else if item.icon === 'stacks'}
+						<IconBox size={18} class="{active ? 'text-[var(--color-brand-600)]' : 'text-[var(--text-tertiary)] group-hover:text-[var(--text-secondary)]'} transition-colors duration-150" />
 					{:else if item.icon === 'deploy'}
 						<IconDeploy size={18} class="{active ? 'text-[var(--color-brand-600)]' : 'text-[var(--text-tertiary)] group-hover:text-[var(--text-secondary)]'} transition-colors duration-150" />
 					{:else if item.icon === 'proxies'}