fix: misleading endpoint status codes and error messages

[jescalada]

Fixes #1285. Based on #1202, would love to get that one merged first!

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[codecov]

Codecov Report

❌ Patch coverage is 73.39450% with 58 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.02%. Comparing base (9f24d3f) to head (b372027).

Files with missing lines	Patch %	Lines
src/service/routes/push.ts	70.14%	20 Missing ⚠️
src/service/routes/auth.ts	77.64%	19 Missing ⚠️
src/service/routes/users.ts	14.28%	6 Missing ⚠️
src/proxy/index.ts	50.00%	5 Missing ⚠️
src/config/index.ts	33.33%	4 Missing ⚠️
...roxy/processors/push-action/checkCommitMessages.ts	92.59%	1 Missing and 1 partial ⚠️
src/service/routes/utils.ts	80.00%	2 Missing ⚠️

❌ Your patch check has failed because the patch coverage (73.39%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1293      +/-   ##
==========================================
- Coverage   83.35%   81.02%   -2.34%     
==========================================
  Files          70       65       -5     
  Lines        3004     4532    +1528     
  Branches      499      775     +276     
==========================================
+ Hits         2504     3672    +1168     
- Misses        397      845     +448     
+ Partials      103       15      -88     

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[jescalada]

I double-checked that the frontend status code handlers are still working. Since we removed a bunch of false 401 errors, most of these would get caught by the generic handler instead.

Of course, we should make these more descriptive by showing the actual error message and status code and removing the callback-based error handling entirely. This is captured in #1188