Add persistent cross-game player bank (Refs #146)

src/lib/server/db/bank.ts

@@ -0,0 +1,27 @@
+import type Database from 'better-sqlite3';
+
+/** No match/server foreign keys: money and idempotency outlive fleet/history cleanup. */
+export function migrateBank(handle: Database.Database): void {
+    handle.exec(`
+        CREATE TABLE IF NOT EXISTS bank_accounts (
+            guid TEXT PRIMARY KEY,
+            balance INTEGER NOT NULL DEFAULT 0 CHECK (typeof(balance) = 'integer' AND balance BETWEEN 0 AND 1000000)
+        );
+        CREATE TABLE IF NOT EXISTS bank_requests (
+            server TEXT NOT NULL, request_id TEXT NOT NULL, guid TEXT NOT NULL,
+            fingerprint TEXT NOT NULL, operation TEXT NOT NULL CHECK (operation IN ('deposit','withdraw')),
+            match_id INTEGER, amount INTEGER NOT NULL DEFAULT 0,
+            state TEXT NOT NULL CHECK (state IN ('prepared','committed','cancelled','rejected')),
+            result TEXT NOT NULL, created_at TEXT NOT NULL, settled_at TEXT,
+            PRIMARY KEY(server, request_id)
+        );
+        CREATE UNIQUE INDEX IF NOT EXISTS bank_pending_guid ON bank_requests(guid) WHERE state = 'prepared';
+        CREATE TABLE IF NOT EXISTS bank_ledger (
+            id INTEGER PRIMARY KEY AUTOINCREMENT, guid TEXT NOT NULL,
+            server TEXT NOT NULL, request_id TEXT NOT NULL, match_id INTEGER,
+            amount INTEGER NOT NULL, balance INTEGER NOT NULL, created_at TEXT NOT NULL,
+            UNIQUE(server, request_id)
+        );
+        CREATE INDEX IF NOT EXISTS bank_ledger_guid ON bank_ledger(guid, id DESC);
+    `);
+}

src/lib/server/db/migrations.ts

@@ -18,6 +18,7 @@ import { migrateAuthSchema, migrateSuperViewerRole } from '../auth/schema.js';
 import { migrateGameFileSchema } from '../game-files/schema.js';
 import { migrateLeaderboardReports } from './leaderboard-reports.js';
 import { migratePlayerScoreTotal } from './player-score-total.js';
+import { migrateBank } from './bank.js';
 import type { Migration } from './migration-runner.js';
 
 // Append only: never renumber entries or change an applied migration to add an
@@ -109,7 +110,8 @@ export const migrations: readonly Migration[] = [
         version: 19,
         name: 'cumulative player score per match',
         run: migratePlayerScoreTotal
-    }
+    },
+    { version: 20, name: 'persistent player bank and transfer ledger', run: migrateBank }
 ];
 
 export const databaseVersion = migrations.length;