Upgrade to axum v0.8

[aumetra]

Upgrade the axum dependency to axum v0.8. Also upgrades base64 to a newer version because why not.

[blueowlgreenfish]

@davidpdrsn I've been wanting to upgrade axum to v0.8, but the incompatibility with axum-flash is in the way. Could you take a look at this?

[mojindri]

Hi @aumetra , thanks for the fix but could this be published,? thanks

[aumetra]

thanks for the fix but could this be published,?

Would love to but I neither have write permissions to the repository nor publish permissions on the crates.io package. So it's stuck in limbo 'til a maintainer gets to it

[damccull]

Would love to get this update too. I'll just use the github branch for now. For others that might want it:

[dependencies]
axum-flash = { git = "https://github.com/davidpdrsn/axum-flash.git", rev = "0832703a0ca83b1ee35daaa8a199f68c2bcb4a90" }