Redesign UI/UX

[AlexandrePTJ]

Some ideas:

• [ ] Text field with completion to select Project / Customer / Activity in one action
• [ ] Ease adding new Project / Customer / Activity with dropdown selection with only a name.
  • Other fields have default values and can be edited later or choose detailed creation (... or + next to new name)
• [ ] Previous timesheets with re-start button
• [ ] Handle dar/light theme
• [ ] Mandatory API token in profile settings