chore(frontend): ballot pages

[kittybest]

Description
The ballot pages logic should be re-designed, since the user could actually submit ballot for multiple times during the voting period.

Currently, if the user already submitted the ballot, the Ballot nav would lead to /ballot/confirmation page, even if the user just add a new project to the ballot and wanna edit the votes.

So the question is:

1. should we split the /ballot and /ballot/confirmation to separate nav tags?
2. if yes, then the timing of displaying each tags should be designated
3. if no, how user check their submitted ballot?

Have a temperate solution in PR #225 , but the whole UX should be re-designed and discussed.