Configurable y-axis tick interval

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: I'm plotting azimuth (degrees on a compass) against time in a time series plot. Using value mappings, I have mapped 0° and 360° to N, 90° to E and so on. But the y-axis has a 25° interval, so it doesn't hit the S, E or W values. For compass degrees, 25° intervals don't make sense. <img width="363" height="557" alt="Image" src="https://github.com/user-attachments/assets/95cf621b-265b-4bc9-b7b7-03e535312c4a" /> (value mappings only done for the yellow axis) **What would you like to be added**: A configuration to fix the y-axis tick interval, in this case to 30°. **Who is this feature for?** For anyone who is struggling with y-axis intervals. I've found some comparable issues in the past, which have been closed, but not resolved. https://community.grafana.com/t/how-to-define-y-axis-ticks-interval/57060 https://community.grafana.com/t/y-axis-values-change-depending-on-time-range/5429/14