feat: rework tfa to display qr code in modals and support easy register / unregister

[Lulalaby]

Example Code:

	[SlashCommand("setup_two_factor", "Setup 2FA")]
	public static async Task SetupTwoFactorAsync(InteractionContext ctx)
		=> await ctx.EnrollTwoFactorAsync();

	[SlashCommand("remove_two_factor", "Remove 2FA"), ApplicationCommandRequireEnrolledTwoFactor]
	public static async Task RemoveTwoFactorAsync(InteractionContext ctx)
		=> await ctx.UnenrollTwoFactorAsync();

easy as that now ^

Example Recording:

Anonymous_2026-01-31.09h39_52_01.mp4

Idea Source:

The idea for displaying the QR in the modal blocktext is from Snazzah (ref: https://canary.discord.com/channels/613425648685547541/1451951249665822780/1466685538886094973)