Fix device seen status sometimes shows "never" even though has

[Steve-Mcl]

Description

Device seen "friendly" text would sometimes show "never" even though just moments ago it said "xx seconds ago"
There are several places in the UI code where a timestamp retrieved from DB is being compared to the browsers Date.now(). Any differences in time between client and server will result in anomalous values.

This PR adds server side computed time device last seen as a milliseconds value. This is transmitted with the device view and can then be safely converted into human readable time period at the frontend.

Related Issue(s)

#1723

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on flowforge/helm to update ConfigMap Template
  • Issue/PR raised on flowforge/CloudProject to update values for Staging/Production

Labels

• [-] Backport needed? -> add the backport label
• [-] Includes a DB migration? -> add the area:migration label

[Steve-Mcl]

@joepavitt, could you do a "pre-review" to ensure the approach is ok with you & if so, I will add unit tests to cover the new data prop lastSeenMs returned by device view?

[joepavitt]

Looks good to me @Steve-Mcl

[Steve-Mcl]

Thanks @joepavitt will get test written later today and re-request for you to check + merge.

[Steve-Mcl]

@joepavitt updated test to ensure new property is present.

Good to go (once tests complete)

[Steve-Mcl]

PG test fails were (it seems) due to GH actions not the code.

3rd time was the charm

Ready for review.