Draft: UI Improvements

Description

As discussed here. The UI of the app needs some improvements. As the previous merge request is already huge and has the purpose of merging upstream changes. I created this MR which focuses on UI improvements according to the mockups provided here.

This merge request needs this to be merged first as the changes done here are based on the code from that MR.

Issue

Current calendar app doesn't follow the design which is given in mockups https://gitlab.e.foundation/e/apps/backlog/-/issues/13

Technical details

These changes in UI make the app look better and moves forward with the design which design team made and therefore having a look which makes it look like an /e/ app by not relying on design choices of upstream app.

Test Procedure

You can download the latest build from here

Light Mode Screenshots

Before	After

Dark Mode Screenshots

Before	After