Add support for Bluesky videos

[huntertur]

Closes #1527

Sample post I've been using for testing: https://bsky.app/profile/srbilyon.stormynights.games/post/3lgjc2n5jac2n

This needs a ./wzl build build-assets due to a change to build.js.

[codecov]

Codecov Report

❌ Patch coverage is 72.41379% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.35%. Comparing base (9b3312d) to head (d5799b6).
⚠️ Report is 424 commits behind head on main.

Files with missing lines	Patch %	Lines
weasyl/embed.py	73.58%	11 Missing and 3 partials ⚠️
weasyl/controllers/detail.py	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1543      +/-   ##
==========================================
+ Coverage   63.13%   63.35%   +0.22%     
==========================================
  Files          95       95              
  Lines        9253     9298      +45     
  Branches     1656     1664       +8     
==========================================
+ Hits         5842     5891      +49     
+ Misses       2925     2910      -15     
- Partials      486      497      +11     

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[huntertur]

(force-push -> rebased following introduction of Deno)