Add screen scaling behavior options

[db39]

The current scaling behavior may not suit some use cases (e.g., on higher-resolution displays). This suggestion came from a user on the forum.

Could we add additional options for scaling behavior? For example:

• No scaling (fixed to the target machine's output resolution)
• Only scale down
• Scale up and down

Related: https://github.com/tiny-pilot/tinypilot/issues/1310

[db39]

Another user on the forum has requested the ability to fix TinyPilot's display to the resolution of the target machine, rather than scaling up/down.