chore: Set up static analysis

[ChristophWurst]

Closes #3765

For code QA. There are existing issues Psalm could locate. Most were fixable. The four remaining ones were added to the baseline.

Todo

• Green CI
• Make static analysis summary a mandatory check

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.41 🎉

Comparison is base (79b3bbf) 22.36% compared to head (c58d5c1) 22.78%.

❗ Current head c58d5c1 differs from pull request most recent head 49e6bd2. Consider uploading reports for the commit 49e6bd2 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5344      +/-   ##
============================================
+ Coverage     22.36%   22.78%   +0.41%     
- Complexity      359      371      +12     
============================================
  Files           236      237       +1     
  Lines         11554    11636      +82     
  Branches       2250     2255       +5     
============================================
+ Hits           2584     2651      +67     
- Misses         8970     8985      +15     

Flag	Coverage Δ
javascript	13.98% <ø> (-0.02%)	⬇️
php	65.50% <ø> (+1.10%)	⬆️

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see 10 files with indirect coverage changes

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