### Summary
- Add Cache-Control headers to all route responses (1h s-maxage, 2h
stale-while-revalidate)
- Append current month to chart data so graphs stay up-to-date
(cumulative carries forward, else zero)
- Remove `.limit(12)` from growth queries for full history
- Pass isCumulative flag through addZeroMonth
- Deduplicate TransformedData type, remove transformRepoStats
This PR is handles the changes required to support envelopes. The new
envelope editor/signing page will be hidden during release.
The core changes here is to migrate the documents and templates model to
a centralized envelopes model.
Even though Documents and Templates are removed, from the user
perspective they will still exist as we remap envelopes to documents and
templates.
