FocusArea: fix checking if already vote, and change button if so
- Fix checking if user already voted. The previous implementation was double-escaping the username (i.e. try a username with "-WMF" in it)
- Have the button say "You've voted!" on page load. We could do like WishlistIntake and query the focus area in init.js, but we'll go the simpler route of using beforeMount() hook for now.
- Fix issues when casting the very first vote (have FocusArea fields default to blank string so that string operations don't error out).
- Add missing word in the 'support-focus-area-confirmed' message.
Bug: T363231