web: Images styles, theming (cherry-pick #19233 to version-2025.12)

[authentik-automation]

Cherry-pick of #19233 to version-2025.12 branch.

Original PR: #19233
Original Author: @GirlBossRush
Cherry-picked commit: d949564

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[netlify]

✅ Deploy Preview for authentik-docs ready!

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.28%. Comparing base (7715ce1) to head (219be15).
⚠️ Report is 1 commits behind head on version-2025.12.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           version-2025.12   #19342      +/-   ##
===================================================
+ Coverage            93.20%   93.28%   +0.08%     
===================================================
  Files                  946      946              
  Lines                52151    52151              
===================================================
+ Hits                 48608    48650      +42     
+ Misses                3543     3501      -42     

Flag	Coverage Δ
e2e	44.68% <ø> (+0.73%)	⬆️
integration	23.45% <ø> (+<0.01%)	⬆️
unit	91.54% <ø> (+<0.01%)	⬆️
unit-migrate	91.59% <ø> (+<0.01%)	⬆️

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[github-actions]

authentik PR Installation instructions

Instructions for docker-compose

Add the following block to your .env file:

AUTHENTIK_IMAGE=ghcr.io/goauthentik/dev-server
AUTHENTIK_TAG=gh-219be15f4782b89ae465c2ae909793f540040893
AUTHENTIK_OUTPOSTS__CONTAINER_IMAGE_BASE=ghcr.io/goauthentik/dev-%(type)s:gh-%(build_hash)s

Afterwards, run the upgrade commands from the latest release notes.

Instructions for Kubernetes

Add the following block to your values.yml file:

authentik:
    outposts:
        container_image_base: ghcr.io/goauthentik/dev-%(type)s:gh-%(build_hash)s
global:
    image:
        repository: ghcr.io/goauthentik/dev-server
        tag: gh-219be15f4782b89ae465c2ae909793f540040893

Afterwards, run the upgrade commands from the latest release notes.