Refactor sluggish endpoints/sql for clickhouse-only "mode"

[alisman]

[immortal71]

@alisman
I’ve implemented an optimization for the sub-issue **#11583 (molecular data endpoint is much slower againstlickHouse) in PR #11840, which is currently open and awaiting review.
As far as I can see, #11583 is the only explicitly defined sub-issue under this Epic, and there is no additional scope described in #11582 itself.​
Once PR #11840 is merged, would you like to keep this Epic open to track any future ClickHouse performance work, or treat it as complete and close it unless new sluggish endpoints are identified?