fix: use templ.NewOnceHandle to prevent script duplication on SSE patches

Replace ConnectionIndicatorWithScript wrapper with a single ConnectionIndicator
component that uses templ.NewOnceHandle() to ensure the watcher script is only
rendered once per page, even when the indicator is patched via SSE.

features/common/components/shared.templ

@@ -52,6 +52,8 @@ func isStale(lastPing int64) bool {
 	return lastPing == 0
 }
 
+var connectionWatcherHandle = templ.NewOnceHandle()
+
 // ConnectionIndicator shows a small dot indicating SSE connection status.
 // Server patches this with a timestamp; client JS detects staleness.
 templ ConnectionIndicator(lastPing int64) {
@@ -79,7 +81,9 @@ templ ConnectionIndicator(lastPing int64) {
 			></div>
 		</div>
 	</div>
-	@connectionWatcher()
+	@connectionWatcherHandle.Once() {
+		@connectionWatcher()
+	}
 }
 
 script connectionWatcher() {