feat(analytics): add Spark batch analytics module

New standalone modules:analytics submodule with two Spark jobs:

- OpeningBookJob: reads game_records.pgn, extracts first N plies using
  pure Catalyst SQL expressions (no UDFs), aggregates win/draw/loss rates
  per opening sequence, writes Parquet + CSV top-1000 summary.

- PlayerStatsJob: unions each game into a player-centric view, aggregates
  total_games/wins/losses/draws/avg_move_count/win_rate per player_id,
  writes Parquet.

Module uses Scala 3 calling spark-sql_2.13 via JVM binary compatibility
(DataFrame API only; no spark.implicits._ / typed Datasets). Spark is
compileOnly; the fat jar bundles only scala3-library + postgresql driver.
Submit via spark-submit; see build.gradle.kts header for invocation.

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

build.gradle.kts

@@ -53,6 +53,8 @@ val coverageExclusions = listOf(
     "**/core/src/main/scala/de/nowchess/chess/resource/GameWebSocketResource.scala",
     // Coordinator infrastructure — gRPC, microservice orchestration
     "**/coordinator/src/main/scala/**",
+    // Analytics module — standalone Spark batch jobs; coverage not applicable (no Quarkus, no scoverage plugin)
+    "modules/analytics/**",
 )
 
 // Converts a Sonar-style glob to a scoverage regex (matched against full source path).