[FEATURE]: better keyboard support

[gianklug]

Is your feature request related to a problem? Please describe.

Currently, timed isn't optimized for keyboard-heavy users. Some examples:

• Having to press tab multiple times after creating a timesheet entry to get to the input box for the next one
• Not being able to switch between tabs, days or pages using the keyboard
• There being no list of supported keyboard shortcuts at the moment

Describe the solution you'd like

This invloves multiple parts:

• More keyboard shortcuts for easier navigation
• A command palette to perform actions or switch to pages, e.g. with Ctrl+K as seen in other tools
• Adding a keyboard shortcut overview

Describe alternatives you've considered

Currently I'm using vimium as an alternative, but this probably won't be the best solution for most people.

Additional context

No response

Required

• I have checked past issues to see if this feature has already been requested.