Change job offers and extra work into list view

Description

• Changes job offers and extra work to an accordion list view
• Combines job offers and applications pages on job-offer/open with two tabs
• Combines extra work and declarations pages on extra-work/open with two tabs
• Made search bars and page titles stack on mobile
• Made header icons now stack and align on mobile as per wireframes
• Makes it possible to accept and retract job offers on the job-offer/open page.
• Fixed bug occurring when applying to 2+ positions in same course edition.

Related Issues

• Resolves #63 (closed)
• Resolves #64 (closed)
• Resolves #45 (closed)
• Resolves #47 (closed)

Checklist

• I have added a changelog entry to reflect the significant changes I made.