[BUG] Improper handling of number rounding

[jeafreezy]

Describe the bug

Currently, production is down due to the improper handling of numbers. This is not happening in development, which means it could be that the backend is not returning a number somewhere.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://fair.hotosm.org.
2. See error.

Expected behavior

Everything should work fine as before.

Screenshots

Desktop (please complete the following information):

• OS: Mac
• Browser: Chrome

[jeafreezy]

It appears that the number rounding is not the major cause of the bug, but rather the assumption that the environment variable 'VITE_MIN_TRAINING_AREA_SIZE' will be a number.

It was configured for the first time in the recent deployment.

It is used here:

fAIr/frontend/src/constants/ui-contents/models-content.ts

Line 124 in ade2132

aoiAreaInstruction: `Area should be > ${formatAreaInAppropriateUnit(MIN_TRAINING_AREA_SIZE)} and < ${formatAreaInAppropriateUnit(MAX_TRAINING_AREA_SIZE)}.`,

Meanwhile formatAreaInAppropriateUnit expects a number:

fAIr/frontend/src/utils/geo/geometry-utils.ts

Lines 39 to 43 in ade2132

	export const formatAreaInAppropriateUnit = (area: number): string => {
	if (area > 1000000) {
	return roundNumber(area / 1000000, 1).toLocaleString() + "km²";
	}
	return roundNumber(area, 1).toLocaleString() + "m²";

The solution will be to better handle environmental variables.