Button validation confirmation

Added confirmation to buttons:

• The back buttons in 1) setting up income and expenses, 2) budget and 3) main menu

Added validation to buttons:

• The next button in budget setup displays an error box if the budget amount has not been used up

changed milestone to %Final product and documentation

added Frontend label

requested review from @andreksv

assigned to @harrylx

approved this merge request

added 1 commit

• 6845c76c - Fixed typos in confirmation messages

Compare with previous version

approved this merge request

merged

mentioned in commit 492a4e69