refactor(web): redo proof of work web worker logic (#941)

* chore(web/js): delete proof-of-work-slow.mjs

This code has served its purpose and now needs to be retired to the
great beyond. There is no replacement for this, the fast implementation
will be used instead.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(web): handle building multiple JS entrypoints and web workers

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(web): rewrite frontend worker handling

This completely rewrites how the proof of work challenge works based on
feedback from browser engine developers and starts the process of making
the proof of work function easier to change out.

- Import @aws-crypto/sha256-js to use in Firefox as its implementation
  of WebCrypto doesn't jump directly from highly optimized browser
  internals to JIT-ed JavaScript like Chrome's seems to.
- Move the worker code to `web/js/worker/*` with each worker named after
  the hashing method and hash method implementation it uses.
- Update bench.mjs to import algorithms the new way.
- Delete video.mjs, it was part of a legacy experiment that I never had
  time to finish.
- Update LibreJS comment to add info about the use of
  @aws-crypto/sha256-js.
- Also update my email to my @techaro.lol address.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(web): don't hard dep webcrypto anymore

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(lib/policy): start the deprecation process for slow

This mostly adds a warning, but the "slow" method is in the process of
being removed. Warn admins with slog.Warn.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(web/js): allow running Anubis in non-secure contexts

Signed-off-by: Xe Iaso <me@xeiaso.net>

* Update metadata

check-spelling run (pull_request) for Xe/purge-slow

Signed-off-by: check-spelling-bot <check-spelling-bot@users.noreply.github.com>
on-behalf-of: @check-spelling <check-spelling-bot@check-spelling.dev>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>
Signed-off-by: check-spelling-bot <check-spelling-bot@users.noreply.github.com>

web/build.sh

@@ -8,7 +8,7 @@ LICENSE='/*
 @licstart  The following is the entire license notice for the
 JavaScript code in this page.
 
-Copyright (c) 2025 Xe Iaso <me@xeiaso.net>
+Copyright (c) 2025 Xe Iaso <xe.iaso@techaro.lol>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -28,6 +28,9 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
+Includes code from https://github.com/aws/aws-sdk-js-crypto-helpers which is
+used under the terms of the Apache 2 license.
+
 @licend  The above is the entire license notice
 for the JavaScript code in this page.
 */'
@@ -36,9 +39,9 @@ for the JavaScript code in this page.
 mkdir -p static/locales
 cp ../lib/localization/locales/*.json static/locales/
 
-esbuild js/main.mjs --sourcemap --bundle --minify --outfile=static/js/main.mjs "--banner:js=${LICENSE}"
-gzip -f -k -n static/js/main.mjs
-zstd -f -k --ultra -22 static/js/main.mjs
-brotli -fZk static/js/main.mjs
-
-esbuild js/bench.mjs --sourcemap --bundle --minify --outfile=static/js/bench.mjs
+for file in js/*.mjs js/worker/*.mjs; do
+  esbuild "${file}" --sourcemap --bundle --minify --outfile=static/"${file}" --banner:js="${LICENSE}"
+  gzip -f -k -n static/${file}
+  zstd -f -k --ultra -22 static/${file}
+  brotli -fZk static/${file}
+done