feat: add hashfs for static asset cache busting and live clock

- Add assets package with dev/prod build tags
- Dev: serve from filesystem with Cache-Control: no-store
- Prod: use hashfs for cache-busting URLs
- Add LiveClock component to show SSE connection status
- Update templates to use StaticPath for asset URLs

features/common/components/shared.templ

@@ -51,8 +51,8 @@ templ NicknamePrompt(returnPath string) {
 // LiveClock shows the current server time, updated with each SSE patch.
 // If the clock stops updating, users know the connection is stale.
 templ LiveClock() {
-	<div class="fixed top-2 right-2 flex items-center gap-1 text-xs opacity-50 font-mono">
-		<div class="status status-xs status-success"></div>
+	<div class="fixed top-2 right-2 flex items-center gap-1.5 text-xs opacity-60 font-mono">
+		<div style="width: 6px; height: 6px; border-radius: 50%; background-color: #22c55e;"></div>
 		{ time.Now().Format("15:04:05") }
 	</div>
 }