fix(ci): run backward-compat test from old code dir to find @prisma/client

- Write test script to /tmp/api-server-old/compat-test.ts instead of /tmp
- Run from /tmp/api-server-old so tsx can resolve node_modules/@prisma/client

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

.gitea/workflows/deploy.yml

@@ -201,7 +201,8 @@ jobs:
             echo "[backward-compat] Skipped — no DB-related changes"
             exit 0
           fi
-          cat > /tmp/compat-test.ts << 'TESTEOF'
+          # Write test inside old code dir so tsx can find node_modules/@prisma/client
+          cat > /tmp/api-server-old/compat-test.ts << 'TESTEOF'
           import { PrismaClient } from '@prisma/client';
           const DB_URL = process.env.DATABASE_URL || '';
           const prisma = new PrismaClient({ datasources: { db: { url: DB_URL } } });
@@ -260,7 +261,8 @@ jobs:
           }
           main().catch(e => { console.error(e); process.exit(1); });
           TESTEOF
-          DATABASE_URL="${{ secrets.DATABASE_URL }}" npx tsx /tmp/compat-test.ts
+          cd /tmp/api-server-old
+          DATABASE_URL="${{ secrets.DATABASE_URL }}" npx tsx compat-test.ts
         env:
           DATABASE_URL: ${{ secrets.DATABASE_URL }}
         timeout-minutes: 5