refactor: static content assets directory

[Schwehn42]

Description

Resolves #4736

Changelog

• Move timer_finished.mp3 and hotkeys.pdf from public to public/assets
• Adjust path refs
• add paths to Caddy and Traefik configs

[Schwehn42]

Q: is /assets or /static better fitting?

[brandstetterm]

Q: is /assets or /static better fitting?

Fine with both

[github-actions]

The deployment to the dev cluster was successful. You can find the deployment here: https://4775.development.scrumlr.fra.ics.inovex.io
This deployment is only for testing purposes and will be deleted after 1 week.
To redeploy rerun the workflow.
DO NOT STORE IMPORTANT DATA ON THIS DEPLOYMENT

Deployed Images

• ghcr.io/inovex/scrumlr.io/scrumlr-frontend:sha-6d9ca17

• ghcr.io/inovex/scrumlr.io/scrumlr-server:sha-6d9ca17

[octomind-dev]

🐙 Octomind

Test Report: 14/14 successful.

description	status	details
About Section Visibility Test	Passed ✅	click
change avatar	Passed ✅	click
check Privacy Policy	Passed ✅	click
check terms & conditions	Passed ✅	click
close cookie banner - front page	Passed ✅	click
close cookie banner - sign-in	Passed ✅	click
create and delete board columns	Passed ✅	click
create_and_delete_notes_and_actions_v2	Passed ✅	click
create lean coffee board	Passed ✅	click
edit_notes_and_actions_v5	Passed ✅	click
get started	Passed ✅	click
share_session	Passed ✅	click
sign-in	Passed ✅	click
test all ways to open the setup flow	Passed ✅	click

commit sha: 6d9ca17