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

migrations/package.json

@@ -0,0 +1,12 @@
+{
+  "private": true,
+  "type": "module",
+  "dependencies": {
+    "pg": "*"
+  },
+  "devDependencies": {
+    "@types/node": "*",
+    "@types/pg": "*",
+    "typescript": "*"
+  }
+}

migrations/provision/postgres/000-init-scores.ts

@@ -0,0 +1,52 @@
+import pg from "pg";
+
+const client = new pg.Client({
+  host: process.env.PROVISION_HOST,
+  port: parseInt(process.env.PROVISION_PORT ?? "5432"),
+  user: process.env.PROVISION_USER,
+  password: process.env.PROVISION_PASSWORD,
+  database: process.env.PROVISION_DATABASE,
+});
+
+await client.connect();
+
+try {
+  await client.query(`
+    CREATE TABLE IF NOT EXISTS players (
+      id TEXT PRIMARY KEY,
+      games_played INT NOT NULL DEFAULT 0,
+      games_won INT NOT NULL DEFAULT 0,
+      games_lost INT NOT NULL DEFAULT 0,
+      best_attempts INT,
+      current_streak INT NOT NULL DEFAULT 0,
+      best_streak INT NOT NULL DEFAULT 0,
+      last_played_at TIMESTAMPTZ,
+      created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+    )
+  `);
+
+  await client.query(`
+    CREATE TABLE IF NOT EXISTS games (
+      id BIGSERIAL PRIMARY KEY,
+      player_id TEXT NOT NULL REFERENCES players(id) ON DELETE CASCADE,
+      target INT NOT NULL,
+      attempts INT NOT NULL,
+      won BOOLEAN NOT NULL,
+      finished_at TIMESTAMPTZ NOT NULL DEFAULT now()
+    )
+  `);
+
+  await client.query(`
+    CREATE INDEX IF NOT EXISTS idx_players_scoreboard
+      ON players (best_attempts NULLS LAST, last_played_at)
+  `);
+
+  await client.query(`
+    CREATE INDEX IF NOT EXISTS idx_games_player_history
+      ON games (player_id, finished_at DESC)
+  `);
+
+  console.log("[txt-game migration-000] score schema created");
+} finally {
+  await client.end();
+}