fix: chunk support issue message stats query to avoid SQL parameter limit

[bernd2022]

Summary

• GET /v1/support/issue/list failed with The incoming request has too many parameters. The server supports a maximum of 2100 parameters when more than ~2100 issues matched the filter.
• Root cause: getMessageStats passed all issue IDs into a single IN (:...ids) clause; TypeORM emits one parameter per ID and SQL Server rejects the query above 2100.
• Fix: chunk the message stats query in batches of 1000 IDs and merge the results into a single map. No API change, identical result set per issue.

Test plan

• npx prettier --check on the changed file
• npx eslint on the changed file
• npm test (927 passed, 0 failed)
• Verify /v1/support/issue/list succeeds on a dataset with >2100 matching issues

[davidleomay]

Could we use Util.doInBatches?