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.

internal/events/bus.go

@@ -24,6 +24,9 @@ const (
 
 	// EventStaticSiteStatus is emitted when a static site status changes.
 	EventStaticSiteStatus EventType = "static_site_status"
+
+	// EventStackStatus is emitted when a compose stack status changes.
+	EventStackStatus EventType = "stack_status"
 )
 
 // Event is a single event published on the bus.
@@ -74,6 +77,14 @@ type StaticSiteStatusPayload struct {
 	Status string `json:"status"`
 }
 
+// StackStatusPayload is the payload for EventStackStatus events.
+type StackStatusPayload struct {
+	StackID string `json:"stack_id"`
+	Name    string `json:"name"`
+	Status  string `json:"status"`
+	Error   string `json:"error,omitempty"`
+}
+
 // Subscriber is a channel that receives events.
 type Subscriber chan Event