fix(test): close leaked database pools in server/tests

[adamsiwiec1]

Summary

Fixes #785 — server/tests files that open a createDatabase pool must give it back.

On main, ~98 files open a pool and only 43 called $client.close(). The other pools stay open for the whole bun test process. With TEST_POOL (max: 2), that sits against PostgreSQL's default 100-connection ceiling, so the next integration tests added fail with sorry, too many clients already for reasons unrelated to their change (as seen on #770).

What changed

1. Close the remaining leaks. For each file that called createDatabase and never closed, added a trailing:

   afterAll(async () => {
     await database.$client.close();
   });

   Registered last so Bun's FIFO afterAll order runs that file's cleanup deletes before the close. Matches the idiom already used in identity-store.integration.test.ts. Files that already used $client.end() were left alone (they already release the pool).

2. Guard test server/tests/database-pool-pairing.test.ts: any file that contains createDatabase( must also contain $client.close( or $client.end(. Pairing rule rather than a lint rule, as proposed in the issue.

3. Sharded runner prose. scripts/test-server-sharded.ts was not on main (it lives on arcade-provider). Restored it with test:server:sharded and corrected the two misleading claims: slots are not exhausted "during the import phase", and the ceiling is not "never a reason to change source". Construction opens 0 connections; the first query takes the pool's max; closing pools is the right fix. Sharding remains useful for wall-clock.

Counts

• 42 files gained a close (had neither close nor end)
• 1 new guard test
• 1 restored/corrected sharded runner + package.json script
• 13 files already using $client.end() unchanged

Test plan

• bun test server/tests/database-pool-pairing.test.ts (pass)
• bun test server/tests/database.test.ts (pass)
• Full bun test server/tests / test:server:sharded with TEST_DATABASE_URL (needs Postgres; not run in this environment)
• CI tests job on this PR