fix(clickhouse): keep IAM-role S3 test TTL within toDateTime range (#4434)

### Problem

`connectors/clickhouse/TestIAMRoleCanIssueSelectFromS3` is failing on
`main` (e.g. [this
run](https://github.com/PeerDB-io/peerdb/actions/runs/27573392839/job/81515384634)).
It loads a 3-row Avro fixture into a raw table and asserts `COUNT(*) ==
3`, but gets `0` — the rows are silently evicted by the table TTL.

### Root cause

#4425 changed the raw-table TTL expression to wrap the timestamp in
`toDateTime()`:

```sql
TTL toDateTime(fromUnixTimestamp64Nano(_peerdb_timestamp)) + INTERVAL N DAY
```

`toDateTime` is a 32-bit type capped at **2106-02-07**. The test
deliberately sets `PEERDB_CLICKHOUSE_RAW_TABLE_TTL_DAYS=36500` (100
years) because the fixture rows carry **2025** timestamps and the
default 90-day TTL would otherwise evict them. With the old `DateTime64`
expression `2025 + 100y ≈ 2125` was fine; with `toDateTime` it overflows
the 2106 ceiling and wraps to a past date, so the TTL evaluates as
already-expired and ClickHouse drops the rows → `COUNT(*) = 0`.

The production default (90 days) never overflows, so this only affects
the test's large override. The backward-compat `toDateTime` fix from
#4425 is left intact.

### Fix

Lower the test's TTL override from 36500 to 25000 days (~68y, lands
around 2093), keeping it within the `toDateTime` range while still
preventing eviction of the 2025 fixture rows. Added a comment explaining
the 2106 ceiling.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dtunikov

flow/connectors/clickhouse/s3_iam_role_test.go

@@ -35,8 +35,10 @@ func TestIAMRoleCanIssueSelectFromS3(t *testing.T) {
 	}
 	internal.SetupFlowAWSCredentialsFromEnv(t)
 	t.Setenv("PEERDB_CLICKHOUSE_AWS_S3_BUCKET_NAME", os.Getenv(bucketNameEnvVar))
-	// Fixture rows have _peerdb_timestamp values from 2025; neuter the raw-table TTL so it doesn't evict them.
-	t.Setenv("PEERDB_CLICKHOUSE_RAW_TABLE_TTL_DAYS", "36500")
+	// Fixture rows have _peerdb_timestamp values from 2025; push the raw-table TTL far enough out that it doesn't
+	// evict them. The TTL expression wraps the timestamp in toDateTime() (a 32-bit type capped at 2106-02-07), so the
+	// 2025 base + INTERVAL must stay under that ceiling; 25000 days (~68y) lands around 2093, comfortably within range.
+	t.Setenv("PEERDB_CLICKHOUSE_RAW_TABLE_TTL_DAYS", "25000")
 	ctx := t.Context()
 
 	conn, err := NewClickHouseConnector(ctx, nil,