fix(ci): downgrade pytest to 8.3.4 for pytest-asyncio compatibility (#20)

pytest-asyncio 0.24.0 requires pytest<9 and >=8.2, but we had pytest==9.0.2 which caused installation conflicts.
Downgrading to pytest==8.3.4 and pytest-cov==6.0.0 to resolve CI test failures.

Author: CervezaStallone

requirements.txt

@@ -52,8 +52,8 @@ Pygments==2.19.2
 pymodbus==3.5.0
 pyOpenSSL==25.3.0
 pyserial==3.5
-pytest==9.0.2
-pytest-cov==7.0.0
+pytest==8.3.4
+pytest-cov==6.0.0
 pytest-django==4.11.1
 python-crontab==3.3.0
 python-dateutil==2.9.0.post0