Use MDI air filter icon for climate entity

[lnagel]

Set the climate entity icon to mdi:air-filter to better represent the ventilation device in the Home Assistant UI.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.57%. Comparing base (152f09f) to head (36432b8).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #155      +/-   ##
==========================================
+ Coverage   90.43%   90.57%   +0.13%     
==========================================
  Files          18       18              
  Lines        1328     1347      +19     
  Branches      127      133       +6     
==========================================
+ Hits         1201     1220      +19     
  Misses         95       95              
  Partials       32       32              

Files with missing lines	Coverage Δ
custom_components/komfovent/climate.py	94.91% <ø> (+0.97%)	⬆️