refactor: Yellow Contrast & Note Tooltip Improvements

[Resaki1]

Description

Improved the color contrast on some elements, especially for the yellow color. Also added/improved some tooltips on the note buttons. Closes #4534.

Changelog

• Darkened all yellow colors
• darker colors for numbers and icons
• removed shadow from vote buttons
• added tooltips for vote buttons
  • changed tooltip text of disabled buttons to show why they are disabled
• removed background of delete and unstack note buttons
• added padding below stacked notes to show the full shadow

Design:
Contrast-issue-yellow.pdf

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• The light- and dark-theme are both supported and tested
• The design was implemented and is responsive for all devices and screen sizes
• The application was tested in the most commonly used browsers (e.g. Chrome, Firefox, Safari)

[Schwehn42]

I didn't check if every single color is correct but all in all it looks great!

[Schwehn42]

lgtm 🟨

[github-actions]

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[octomind-dev]

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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: 0896d74