Add visual smoothing for snake game and systemd deployment

CSS animations for smoother 60fps feel despite 7Hz game ticks:
- 130ms transitions on cell background/box-shadow
- Head pop-in animation on direction changes
- Food pulse animation
- Smooth death state fade with grayscale

Per-snake colored glow on head cells.

Make server port configurable via PORT env var (default 8080).

Add deploy/ with systemd service and scripts:
- setup.sh: create games user, /opt/c4, install unit
- deploy.sh: build and install binary, restart service
- package.sh: cross-compile, tarball, base64 split for transfer
- reassemble.sh: decode and extract on target server

main.go

@@ -6,6 +6,7 @@ import (
 	_ "embed"
 	"log"
 	"net/http"
+	"os"
 
 	"github.com/google/uuid"
 
@@ -20,9 +21,11 @@ import (
 	"github.com/ryanhamamura/via/vianats"
 )
 
-var store = game.NewGameStore()
-var snakeStore = snake.NewSnakeStore()
-var queries *gen.Queries
+var (
+	store      = game.NewGameStore()
+	snakeStore = snake.NewSnakeStore()
+	queries    *gen.Queries
+)
 
 //go:embed assets/css/output.css
 var daisyUICSS []byte
@@ -35,6 +38,13 @@ func DaisyUIPlugin(v *via.V) {
 	v.AppendToHead(h.Link(h.Rel("stylesheet"), h.Href("/_plugins/daisyui/style.css")))
 }
 
+func port() string {
+	if p := os.Getenv("PORT"); p != "" {
+		return p
+	}
+	return "7331"
+}
+
 func main() {
 	if err := db.Init("c4.db"); err != nil {
 		log.Fatal(err)
@@ -60,7 +70,7 @@ func main() {
 	v.Config(via.Options{
 		LogLevel:       via.LogLevelDebug,
 		DocumentTitle:  "Game Lobby",
-		ServerAddress:  ":7331",
+		ServerAddress:  ":" + port(),
 		SessionManager: sessionManager,
 		PubSub:         ns,
 		Plugins:        []via.Plugin{DaisyUIPlugin},