Updates `examples/demo` to Next.js 15 and adds Next.js 15 support to `packages/stack`.
The other packages and apps are still running on Next.js 14 to ensure compatibility.
* added magic link email, updated email template
* added magic link ui and db schema
* restructured sign in sign up page
* updated example custom button
* added joy tabs
* fixed bugs, added magic link errors, abstracted token creation
* added magic link callback
* fixed token bugs
* added more auth information to user object
* added changeset
* added stack-ui package
* added ui elements
* fixed react package type bug, added deleted components back
* updated button and typography interface
* added element provider
* moved all elements to element context
* added ui-joy
* moved UIPage component and update Button component
* added StackUIProvider
* added UI framework switch
* changed theme to colormode
* changed StackUIProvider interface
* updated file names
* updated package config
* fixed types and dependencies
* fixed color theme
* added custom button
* converted signin page to stack-ui
* moved oauth button stack-ui
* fixed styling bugs
* changed color/variant interface for button and text
* moved credential sign up to stack-ui
* moved card header and divider to stack-ui
* moved card-frame to stack-ui, fixed bugs
* fixed bugs, added global bg color to dev app
* moved forgot password to stack-ui
* updated styling
* moved form warning text to stack-ui
* added redirect message card to stack-ui
* moved everything to stack-ui, removed daisy and tailwind
* added joy input
* simplified code
* fixed joy button
* restructured UI provider interface
* made joy color mode work
* fixed small ui bugs
* updated demo, changed constant structures in stack-ui
* added select ui to demo
* added joy ui text
* added mui divider
* Used dynamic elements to replace useElements hook
* changed full page behaviour (100vh => 100%)
* added auto detect parent to cardframe
* updated documentation
* updated customization overview
* updated custom color doc
* fixed system color mode bug
* fixed select visual on safari
* changed UI provider interface
* renamed files to lower case
* fixed import bug
* finished custom colors doc
* added docs for custom components
* removed wrong cased files
* updated custom pages docs
* updated custom component docs
* elements -> components
* fixed missing rename
* fixed broken links in docs
* removed tailwind css import in stack
* fixed typos and small problems
* cleaned up package.json files
* updated dependencies
* fixed stack-server bug (webpack xxx not a function and u type error)
* updated setup doc
* added changeset
* fixed the 'use client' bug in stack-ui
* merged stack-ui and stack-ui-joy into stack
* renamed StackUIProvider to StackTheme
* unified imports
* added hook details to custom color doc
