feat(server): Http4s server

Changed at how the run command starts TUI GUI and the server. This is neccessary so that TUI GUI and server start and the game from the TUI/GUI is registered in the server.

build.gradle.kts

@@ -40,3 +40,7 @@ val versions = mapOf(
 )
 extra["VERSIONS"] = versions
 
+tasks.register("run") {
+    dependsOn(":modules:ui:run")
+}
+

modules/server/src/main/scala/de/nowchess/server/ServerLauncher.scala

@@ -0,0 +1,25 @@
+package de.nowchess.server
+
+import cats.effect.IO
+import cats.effect.unsafe.implicits.global
+import com.comcast.ip4s.{host, port}
+import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.chess.engine.GameEngine
+import org.http4s.ember.server.EmberServerBuilder
+
+object ServerLauncher:
+  def start(engine: GameEngine): String =
+    val white = PlayerInfo(PlayerId("white"), "Player 1")
+    val black = PlayerInfo(PlayerId("black"), "Player 2")
+    (for
+      registry <- GameRegistry.make
+      _        <- EmberServerBuilder
+                    .default[IO]
+                    .withHost(host"0.0.0.0")
+                    .withPort(port"8080")
+                    .withHttpApp(BoardRoutes(registry).routes.orNotFound)
+                    .build
+                    .useForever
+                    .start
+      gameId   <- registry.add(GameEntry(engine, white, black))
+    yield gameId).unsafeRunSync()

modules/ui/build.gradle.kts

@@ -64,6 +64,7 @@ dependencies {
     implementation(project(":modules:rule"))
     implementation(project(":modules:api"))
     implementation(project(":modules:io"))
+    implementation(project(":modules:server"))
 
     // ScalaFX dependencies
     implementation("org.scalafx:scalafx_3:${versions["SCALAFX"]!!}")

modules/ui/src/main/scala/de/nowchess/ui/Main.scala

@@ -1,21 +1,22 @@
 package de.nowchess.ui
 
 import de.nowchess.chess.engine.GameEngine
+import de.nowchess.server.ServerLauncher
 import de.nowchess.ui.terminal.TerminalUI
 import de.nowchess.ui.gui.ChessGUILauncher
 
 /** Application entry point - starts both GUI and Terminal UI for the chess game.
  *  Both views subscribe to the same GameEngine via Observer pattern.
+ *  The REST server shares the same engine instance, so API moves are reflected in the UI.
  */
 object Main:
   def main(args: Array[String]): Unit =
-    // Create the core game engine (single source of truth)
     val engine = new GameEngine()
+    val gameId = ServerLauncher.start(engine)
+    println(s"REST API ready — game ID: $gameId  →  http://localhost:8080/api/board/game/$gameId")
 
-    // Launch ScalaFX GUI in separate thread
     ChessGUILauncher.launch(engine)
 
-    // Create and start the terminal UI (blocks on main thread)
     val tui = new TerminalUI(engine)
     tui.start()