refactored e2e-tests, splitted up in multiple tests and simplified them

[framitdavid]

Description

I've split the tests into multiple smaller tests to avoid timeouts with Playwright. Additionally, I've optimized the tests by critically assessing how things are tested in Gitea. As a result, I can now consistently run the tests against the development environment from localhost. The next step is to verify if they run equally well in the pipeline.

Related Issue(s)

• PR itself

Verification

• [x] Your code builds clean without any errors or warnings
• [x] Manual testing done (required)
• [x] Relevant automated test added (if you find this hard, leave it and we'll help out)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.78%. Comparing base (7e5236c) to head (72167de).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #13025 +/- ## ======================================= Coverage 91.78% 91.78% ======================================= Files 1400 1400 Lines 19827 19827 Branches 2388 2388 ======================================= Hits 18199 18199 Misses 1371 1371 Partials 257 257 ```

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