feat: refactor database connection handling and add legacy map loading functionality

- Updated check-connections.mts to use Prisma with PostgreSQL adapter.
- Introduced databaseUrl.ts for resolving database URLs from environment variables.
- Added legacyMapLoader.ts to load and parse legacy map data.
- Implemented scenarioSeeder.ts to seed scenario data into the database.
- Created tests for scenario seeding in scenarioSeeder.test.ts.
- Configured Prisma datasource in prisma.config.ts to support dynamic database URLs.

app/game-engine/test/scenarioSeeder.test.ts

@@ -0,0 +1,71 @@
+import { createPostgresConnector } from '@sammo-ts/infra';
+
+import { resolveDatabaseUrl } from '../src/scenario/databaseUrl.js';
+import { seedScenarioToDatabase } from '../src/scenario/scenarioSeeder.js';
+
+const scenarioId = 1010;
+const databaseUrl = await resolveDatabaseUrl();
+
+const canConnectToDatabase = async (url: string): Promise<boolean> => {
+    const connector = createPostgresConnector({ url });
+    try {
+        await connector.connect();
+        await connector.prisma.$queryRawUnsafe('SELECT 1');
+        return true;
+    } catch {
+        return false;
+    } finally {
+        await connector.disconnect();
+    }
+};
+
+const canRun = await canConnectToDatabase(databaseUrl);
+const describeDb = describe.runIf(canRun);
+
+describeDb('scenario database seed', () => {
+    test('writes scenario data into tables', async () => {
+        const { seed } = await seedScenarioToDatabase({
+            scenarioId,
+            databaseUrl,
+        });
+
+        const connector = createPostgresConnector({ url: databaseUrl });
+        await connector.connect();
+        try {
+            const prisma = connector.prisma;
+            const [
+                nationCount,
+                cityCount,
+                generalCount,
+                diplomacyCount,
+            ] = await Promise.all([
+                prisma.nation.count(),
+                prisma.city.count(),
+                prisma.general.count(),
+                prisma.diplomacy.count(),
+            ]);
+
+            expect(nationCount).toBe(seed.nations.length);
+            expect(cityCount).toBe(seed.cities.length);
+            expect(generalCount).toBe(seed.generals.length);
+            expect(diplomacyCount).toBe(seed.diplomacy.length);
+            expect(generalCount).toBeGreaterThan(0);
+
+            if (seed.diplomacy.length > 0) {
+                const sample = seed.diplomacy[0];
+                const row = await prisma.diplomacy.findFirst({
+                    where: {
+                        srcNationId: sample.fromNationId,
+                        destNationId: sample.toNationId,
+                    },
+                });
+                expect(row).not.toBeNull();
+                if (row) {
+                    expect(row.stateCode).toBe(sample.state);
+                }
+            }
+        } finally {
+            await connector.disconnect();
+        }
+    });
+});