loading up issues on @tangled.sh/core should be much faster because we
only have to resolve ~10 DIDs at a time. with a saturated did-handle
cache, this should be near-instant page load times.

follows our diff fragment colorscheme now

and move appview/state/settings to appview/settings

move settings router into a subpackage

also introduces a middleware package under appview, and turns TID() into
a global function that operates on a globally mutable TID clock.

PRs are no longer merged as a single commit.