Apply Styling per Design Spec (Suggestion Form)

[marcbachan]

Description

Align modal and field layout with design wireframes. Requires input from @lxh5395 for target design.

Complexity

~50 LOC; CSS module updates

[marcbachan]

Per weekly meeting - reuse the "add" modal for the suggestion form. Some of the fields will be greyed out, which will be relevant for implementation of #649.