feat: update connection pages

[lucas-louis]

Description

• Update the connection, login & signup pages
• Remove old variants & sizes on both text & button theme

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the needed labels
• I have linked this PR to an issue
• I have linked this PR to a milestone
• I have linked this PR to a project
• I have tested this code
• I have added / updated tests (unit / functionals / end-to-end / ...)
• I have updated the README and other relevant documents (guides...)
• I have added sufficient documentation both in code, as well as in the READMEs

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