feat(db): provision Postgres and add score schema migration

Wire in the txt_game_scores database provision and create the
players/games tables via a provision-scoped migration so Child 2
can implement the server-side score persistence.

- module.yml: requires postgres database (txt_game_scores) with
  env_map for host/port/user/password/name; empty env keys added
  so env-sync populates them after provisioning
- migrations/package.json: ESM, pg + typescript devdeps
- migrations/provision/postgres/000-init-scores.ts: creates
  players and games tables with idempotent IF NOT EXISTS guards
  and two supporting indexes (scoreboard sort, history lookup)

Server code, Dockerfile, and docker-compose.yml are unchanged —
server integration is deferred to the follow-on child task.

Task: 3dab55e3-9792-47a0-a4a6-ba7757517314

module.yml

@@ -11,7 +11,23 @@ docker:
     context: .
     dockerfile: Dockerfile
 
+requires:
+  - provider: postgres
+    type: database
+    name: txt_game_scores
+    env_map:
+      TXT_GAME_DB_HOST: host
+      TXT_GAME_DB_PORT: port
+      TXT_GAME_DB_USER: user
+      TXT_GAME_DB_PASSWORD: password
+      TXT_GAME_DB_NAME: database
+
 env:
   DOMAIN:
     from: node.domain
     default: localhost
+  TXT_GAME_DB_HOST:
+  TXT_GAME_DB_PORT:
+  TXT_GAME_DB_USER:
+  TXT_GAME_DB_PASSWORD:
+  TXT_GAME_DB_NAME: