Ensure users know when we can't store their Vault locally

[luckyrat]

Users in a Private browsing window (and maybe under other rare configurations) need to be made aware that this prevents Kee Vault from storing information and therefore prevents them from accessing their Kee Vault when they have no network connection.

Since reliably detecting a private browsing window is always going to be a difficult feature to maintain and risks categorisation as an invasion of privacy, despite the noble intentions, we must instead notify all users that have signed in to a device where we do not have any locally stored data...

• Wait until settings sync has completed after user sign-in.
• If a user signed in via the intro page "Existing users" button or link and they do not have the setting enabled to disable this feature:
• Render a notification (bell icon?) in the footer. On mobile it can be included in the "more" menu initially but in future (or if easy initially) it should be included on the footer whenever there is sufficient space.
• Clicking the icon should display a "Notifications" panel which contains a single notification (at least on desktop). If there is not enough space on mobile for this we need to render a separate view with a close/cross button and OK button - possibly an alert, but I don't think these are scrollable so will need to experiment to find the right approach.
• Contents of the notification should be:

First sign-in

This is the first time you've signed in to Kee Vault on this device.

Not correct?

If this notification keeps appearing on your device you are probably accessing Kee Vault using a device or web browser that is preventing Kee Vault from storing information.

Kee Vault needs to store information for many features to work correctly, including offline access to your Kee Vault!

We've prepared a help topic to explain more about the need for storing this information and what you can do to enable it.

For a quick fix, try disabling Private browsing / incognito mode and this message should stop appearing after you've signed in a couple of times.

• New general setting, enabled by default:

[ ] Show a notification when you first sign in to Kee Vault on a device

When disabled, render warning text underneath:
[!] This notification makes you aware that your device is not able to offer offline access to your Vault. We recommend you leave this setting ENABLED unless you have a strong understanding of what can cause this and are happy to accept the risk of unexpected temporary loss of access to your Vault.