[FE] Create a protection layer to preserve for the case when we need to upgrade/fix

[hnngo]

Currently, while we are fixing the production site, users still can access our website and this may cause some interrupted user experiences and easily prone to error/weird bugs. We need to have a way to figure out how to protect our website by adding a layer stating for the purpose like "We are upgrading our system, please come back later!"

[hnngo]

First task already done - created protection layer #161

Pending actions:

1. Getting support from BE to add new API that can read/write data for maintanance
2. Integrate with FE