feat: add connection status indicator with SSE heartbeat

- Add ConnectionIndicator component showing green/red dot
- Send lastPing signal every 15 seconds via SSE
- Indicator turns red if no ping received in 20 seconds
- Gives users confidence the live connection is active

features/c4game/handlers.go

@@ -1,6 +1,7 @@
 package c4game
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"strconv"
@@ -17,7 +18,6 @@ import (
 	"github.com/ryanhamamura/games/db/repository"
 	"github.com/ryanhamamura/games/features/c4game/pages"
 	"github.com/ryanhamamura/games/sessions"
-	appsse "github.com/ryanhamamura/games/sse"
 )
 
 // c4ChatColors maps player color (1=Red, 2=Yellow) to CSS background colors.
@@ -120,7 +120,8 @@ func HandleGameEvents(store *connect4.Store, nc *nats.Conn, sm *scs.SessionManag
 		}
 
 		sendPing := func() error {
-			return appsse.SendPing(sse)
+			ping, _ := json.Marshal(map[string]int64{"lastPing": time.Now().UnixMilli()})
+			return sse.PatchSignals(ping)
 		}
 
 		// Send initial render and ping

features/snakegame/handlers.go

@@ -1,6 +1,7 @@
 package snakegame
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"strconv"
@@ -16,7 +17,6 @@ import (
 	"github.com/ryanhamamura/games/features/snakegame/pages"
 	"github.com/ryanhamamura/games/sessions"
 	"github.com/ryanhamamura/games/snake"
-	appsse "github.com/ryanhamamura/games/sse"
 )
 
 func snakeChatColor(slot int) string {
@@ -126,7 +126,8 @@ func HandleSnakeEvents(snakeStore *snake.SnakeStore, nc *nats.Conn, sm *scs.Sess
 		}
 
 		sendPing := func() error {
-			return appsse.SendPing(sse)
+			ping, _ := json.Marshal(map[string]int64{"lastPing": time.Now().UnixMilli()})
+			return sse.PatchSignals(ping)
 		}
 
 		// Send initial render and ping

sse/signals.go

@@ -1,28 +0,0 @@
-// Package sse provides helpers for SSE signal handling.
-package sse
-
-import (
-	"encoding/json"
-	"time"
-
-	"github.com/starfederation/datastar-go/datastar"
-)
-
-// Signals holds client-side state managed via SSE.
-type Signals struct {
-	LastPing int64 `json:"lastPing,omitempty"`
-}
-
-// SendPing sends a heartbeat signal with the current timestamp.
-func SendPing(sse *datastar.ServerSentEventGenerator) error {
-	return PatchSignals(sse, Signals{LastPing: time.Now().UnixMilli()})
-}
-
-// PatchSignals sends a signals patch to the client.
-func PatchSignals(sse *datastar.ServerSentEventGenerator, s Signals) error {
-	data, err := json.Marshal(s)
-	if err != nil {
-		return err
-	}
-	return sse.PatchSignals(data)
-}