fix: saveable share qr code

[Schwehn42]

Description

Makes the QR code available in the share view saveable as a file. Note this works for FF and Chrome, but not Safari for me, seems to be a limitation on their part so I won't be bothered 🫣
Closes #4170

Changelog

ShareSession

• change QR code render type from svg to canvas (makes it saveable)
• increase render size 10-fold (otherwise it's blurry)

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)

(Optional) Visual Changes

[brandstetterm]

The QR code doesn't look that nice in dark mode anymore :/

Before:

After:

[Schwehn42]

@brandstetterm seems like qrcode.react doesn't support setting colors directly using CSS. The workaround used until this point was changing the fill of the svg, however, this isn't possible anymore since we're using a canvas now. Different libraries like https://github.com/rosskhanas/react-qr-code have the same issue. There are two ways to go on about this:

1. set fgColor and bgColor of element manually using the retreived attribute theme (JSX)
2. invert color of whole class using the filter function if [theme='dark'] (CSS)

I opted for using 1.,but am open for the other option as well.

EDIT (2024-07-17):

Using the new theme state hook introduced in #4310, the current theme is now detected and applied to the QR Code.

[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: c692f8b

[mateo-ivc]

lgtm

[github-actions]

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