feat(api): define shared EventEnvelope and EventType for Redis EventBus (#61)

- Add EventEnvelope case class (eventId, type, payload, timestamp, correlationId)
- Add EventType enum with all known event types
- Update account EventPublisher to use EventEnvelope instead of raw string interpolation
- Add EventEnvelope/EventType to account NativeReflectionConfig
- Add Jackson Scala and JSR310 modules to api dependencies
- Add api module dependency to account module
- Add NativeReflectionConfig rule to CLAUDE.md

Closes NCS-90
https://knockoutwhist.youtrack.cloud/issue/NCS-90

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Reviewed-on: #61

modules/api/build.gradle.kts

@@ -50,6 +50,8 @@ dependencies {
         }
     }
     implementation("com.fasterxml.jackson.core:jackson-databind:${versions["JACKSON"]!!}")
+    implementation("com.fasterxml.jackson.module:jackson-module-scala_3:${versions["JACKSON_SCALA"]!!}")
+    implementation("com.fasterxml.jackson.datatype:jackson-datatype-jsr310:${versions["JACKSON"]!!}")
 
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")

modules/api/src/main/scala/de/nowchess/api/event/EventEnvelope.scala

@@ -0,0 +1,27 @@
+package de.nowchess.api.event
+
+import com.fasterxml.jackson.databind.JsonNode
+import java.time.Instant
+import java.util.UUID
+
+final case class EventEnvelope(
+    eventId: UUID,
+    `type`: EventType,
+    payload: JsonNode,
+    timestamp: Instant,
+    correlationId: Option[String],
+)
+
+object EventEnvelope:
+  def of(
+      `type`: EventType,
+      payload: JsonNode,
+      correlationId: Option[String] = None,
+  ): EventEnvelope =
+    EventEnvelope(
+      eventId = UUID.randomUUID(),
+      `type` = `type`,
+      payload = payload,
+      timestamp = Instant.now(),
+      correlationId = correlationId,
+    )

modules/api/src/main/scala/de/nowchess/api/event/EventType.scala

@@ -0,0 +1,4 @@
+package de.nowchess.api.event
+
+enum EventType:
+  case GameStart, GameCreationRequest, GameCreationResponse, BotGameStart, ChallengeCreated, ChallengeAccepted

modules/api/src/test/scala/de/nowchess/api/event/EventEnvelopeTest.scala

@@ -0,0 +1,50 @@
+package de.nowchess.api.event
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class EventEnvelopeTest extends AnyFunSuite with Matchers:
+
+  private val mapper =
+    val m = new ObjectMapper()
+    m.registerModule(DefaultScalaModule)
+    m.findAndRegisterModules()
+    m
+
+  test("EventEnvelope round-trips through JSON") {
+    val payload = mapper.createObjectNode()
+    payload.put("gameId", "game-123")
+    payload.put("difficulty", 3)
+
+    val original = EventEnvelope.of(EventType.GameStart, payload, Some("corr-abc"))
+
+    val json    = mapper.writeValueAsString(original)
+    val decoded = mapper.readValue(json, classOf[EventEnvelope])
+
+    decoded.eventId shouldBe original.eventId
+    decoded.`type` shouldBe original.`type`
+    decoded.payload shouldBe original.payload
+    decoded.timestamp shouldBe original.timestamp
+    decoded.correlationId shouldBe Some("corr-abc")
+  }
+
+  test("EventEnvelope serializes without correlationId") {
+    val payload = mapper.createObjectNode()
+    payload.put("challengeId", "ch-1")
+
+    val envelope = EventEnvelope.of(EventType.ChallengeCreated, payload)
+    val json     = mapper.writeValueAsString(envelope)
+    val decoded  = mapper.readValue(json, classOf[EventEnvelope])
+
+    decoded.`type` shouldBe EventType.ChallengeCreated
+    decoded.correlationId shouldBe None
+  }
+
+  test("EventEnvelope.of generates unique eventIds") {
+    val payload = mapper.createObjectNode()
+    val e1      = EventEnvelope.of(EventType.BotGameStart, payload)
+    val e2      = EventEnvelope.of(EventType.BotGameStart, payload)
+    e1.eventId should not equal e2.eventId
+  }