add level and level_progress to stats api routes

[HorizonCode]

Describe your changes

• Adds level and level_progress to stats routes

Checklist

• [x] I've manually tested my code

[minisbett]

I'm not sure whether this is a concern for bpy or whether a frontend should implement this itself

[tsunyoku]

level is a statistic so i don't have an issue with this being provided via API

[7ez]

tbh would be cooler if level and level progress would be combined

[tsunyoku]

i'm not convinced we need all 3. level being a float with the decimals being the progress should be enough

i don't particularly care which we pick, but either have level and progress separated or have them combined into one float. but not both

[HorizonCode]

then i would say keep level and level progress, bc for frotend dev its easier to use the values