db/limits: Limit SQL query results

At the RPC level we do have the notion of `too_many_entries`, however, to come to the decision we already did a full SQL query of i.e. all assets.

## Proposal

Limit the SQL queries to `N+1` entries, where `N` is the maximum number we would return without yielding a `too_many_entries` response to the requester. That way we don't burn CPU cycles on very large assets.