Scroll List, Darkmode, small fixes

[ebert-l]

User Liste ist jetzt alleine scrollbar, ohne die Navigation weg zu scrollen.

[ebert-l]

Darkmode kann gestartet werden, wenn man auf den Bierkrug oben links klickt

[maseiler]

Very nice work! I'd love to have a few quick fixes before I merge it into production:

• General:
  • change user selection color t(yellow is an indicator, that a user's account is almost full)
  • a dedicated switch button in NavBar
    • e.g. this icon or something else
  • Feedback button: white font
• Home page:
  • only half of the page has enabled dark mode
• Statistic page:
  • sidebar: white font
  • background
• admin page:
  • sidebar: white font
  • User/Item/Booking list: white font for field ID
  • Feedback: ID , Timestamp white font
  • Feedback: text fields still white

Feature request

• adjust automatically based on current time

[ebert-l]

All Fixes are now implemented. The feature Request with the time-based color switching will be provided as a seperate merge.

[ebert-l]

Time based switching is now implemented. Check-Interval is set to 10s. The manual switch is obsolete with automatic switching enabled. Therefore the switch is no longer visible while using time based theme switching. If you want to disable automatic mode and go back to manual switching, you just need to change the value of 'automaticThemeSwitching' to false in NavBar.vue

[ebert-l]

Too many changes in one PR. I will separate the changes in three different PRs.