feat: return indicators in Issue API
cleanup: remove /compare

Can reinstate later if we need it again
cleanup: remove person-party comparison
cleanup: remove /parties.html

There’s no current plan to have per-party Stance pages on TWFY, so
remove this for now.
cleanup: remove /party/:id

No need for an individual party page for now either
cleanup: group functions better

Just rearranging things — nothing added or removed.
fix: issue_stances should use passed issue

issue, not @issue