feat(server): restructure Pomodoro server into modular components

- move server logic to cmd/server/main.go
- create packages for websocket, pomodoro and broadcast handling
- define models for messages
- remove old GoTomato.go file
- update README

🤖

cmd/server/main.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"git.smsvc.net/pomodoro/GoTomato/internal/websocket"
+	"log"
+	"net/http"
+)
+
+func main() {
+	http.HandleFunc("/ws", websocket.HandleConnections)
+
+	log.Println("Pomodoro WebSocket server started on :8080")
+	err := http.ListenAndServe(":8080", nil)
+	if err != nil {
+		log.Fatalf("Error starting server: %v", err)
+	}
+}