chore(www): migrate root .well-known/ to www/.well-known/ (#383)

Refs rsr-template-repo#119 (stage 5).

Moves the root `.well-known/` bundle to the canonical
`www/.well-known/`.
Pure rename, no content change.

Opened and merged directly because this repository's ruleset for `main`
requires changes to go through a pull request. The branch was produced
by `scripts/sweep-wellknown.sh` and verified as an exact rename.

Co-authored-by: stage5-sweep <stage5-sweep@users.noreply.github.com>

Author: hyperpolymath