parsemail v2.0.0

* Fix the release stack: fail-fast diagnostics and pinned DNS (1bf6c67)
* Make every smoke-test wait visible (d79c9a6)
* Fix the release gates: key import and when:always (a3f11e2)
* Match tag signatures against the primary key or its signing subkey (f3b1c05)
* Require a buffering proxy, and bound upload size (dad08e9)
* Improved CI and release process and greatly shrunk image (f350cd0)
* Ship as a PyInstaller bundle on a scratch base (2848eec)
* Run the parsemail container unprivileged and read-only (b5b5c44)
* Use geoveto for IP geolocation (dfdba3c)
* Use tonguepipe for translation (f2b9de7)
* Messages about rendered html differences, especially in dark mode (166f749)
* Switch to using external parsemail-renderer image for html rendering (8acafa0)