Remove phpdbg from coverage target

[ohmyfelix]

Summary

Replace the coverage target in Makefile to run Tester with php instead of phpdbg.

Motivation

This aligns contributte/comgate with contributte/contributte#73 so coverage runs no longer depend on phpdbg.

Changes

• switch both coverage target variants from -p phpdbg to -p php

Testing

• make coverage attempted locally
• Coverage run completes locally
• CI passes

Local blocker: on PHP 8.5.3, make coverage currently fails inside nette/tester with Using null as an array offset is deprecated in vendor/nette/tester/src/Framework/Dumper.php:422 before coverage output is produced.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.81%. Comparing base (137d851) to head (66ded55).
⚠️ Report is 10 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (137d851) and HEAD (66ded55). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (137d851)	HEAD (66ded55)
	5	2

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #53      +/-   ##
==========================================
- Coverage   67.18%   60.81%   -6.38%     
==========================================
  Files          15       15              
  Lines         256      222      -34     
==========================================
- Hits          172      135      -37     
- Misses         84       87       +3     

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