Cleanup style and classes

Intro

You could think this user story is an ongoing project, but it is specifically to solve technical style debt found in the review of #391. Reason? The program of Imagine 2024 is published, no time for technical debt!

Requirements

[ ] Centralize common style in .cell-dropdown-content and .sticky-modest-drop-t-head-content
[ ] Move the style from case width: 25%; below to a (new) class in the style sheet
[ ] Move the style from case Modest dropdown below to a (new) class in the style sheet
[ ] Move the style combined with modest-dropdown-content to a (new) class in the style sheet
[ ] Cleanup more style and classes if you feel like it

Case elaborations

`width: 25%`

<input type="submit" name="{{ action }}_canceled" value="No please cancel"
    style="width: 25%;"/>
<span class="warning-input">
    <input type="submit" name="{{ action }}_confirmed" value="Sure"
        style="width: 25%;"/>

Modest dropdown

<span class="active-text" style="color: var(--modestStandoutColor);">
    Fan
</span>
<div class="sticky-modest-drop-t-head-content">
    <table style="min-width: 12rem;">

`modest-dropdown-content`

<div class="modest-dropdown-content" style="background-color: black; cursor: default; min-width: 350px">
<div class="modest-dropdown-content" style="min-width: 350px">

maar35 / film-festival-planner