feat: display when the next check will happen as a heartbeat timer

[mohit-nagaraj]

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Description

1. navigating to other pages and coming back to this one will still have the timer to continue
2. update the timer when monitor is paused and played back
3. reset the timer when a ping is made based on whenever it makes (keeps it consistnent cuz heartbeat & heart retry can be at different times hence reset it whenever request is made

Fixes #5120

Type of change

Please delete any options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas (including JSDoc for methods)
• My changes generates no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

added all test cases to work

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[CommanderStorm]

I have left some comments below

[louislam]

Based on your description, this pr might be going into an incorrect direction, and this pr could be much difficult to be implemented that you think. We should have a discussion before we go.

Some points come in my mind:

• It can't be frontend only, because frontend can never know the next check time.
• Use this.lastHeartBeat.end_time to "guess" the next check time won't work.
• Uptime Kuma is a socket.io application, a monitor could be changed by another browser at the same time.
• Restart Uptime Kuma also affect it.

And actually, I have a plan to change the core to Croner (#3447)

Croner provides the next run time, which fits for this pr:

job.nextRun( /*optional*/ startFromDate );	// Get a Date object representing the next run.

I would suggest that this pr should be based on #3447

[mohit-nagaraj]

Hey @louislam i do get your point. The thing is since the lastheart gets updated whenever we change the interval (even from other browser, all the related data about it also gets updated. Below is a video attached for ur reference.

Video link - https://www.loom.com/share/65820c1c0e624839ac0f7cce6fa78982

[CommanderStorm]

FYI: pinging me daily will not get your PRs reviewed and merged quicker.
On the contrary: being annoying usually has the opposite effect of pushing your PR to the back of peoples queues.

If it has been a month and you think your PR has been forgotten, fine... but daily?...

[louislam]

Please read our pull request rules, rushing is not allowed.

And I think you didn't get my point of my previous comment, frontend only timer must be wrong in some cases, because only backend knows the actual next check time.

You video didn't cover all possible cases unfortunately.

[mohit-nagaraj]

Hey first of all i am sorry if it disturbed you a lot. I didnt meant to to cause any trouble to you guys. Secondly, All i was expecting was some communication from you guys stating "sure" "will check it". Since days were passing without any information, I thought this pr is becoming stale. I didnt want to be a trouble in your already busy schdule. Third, if you want more video content covering all test cases do let me know. I wanted to just show for that case. Alternatively if required, you can post the ones which fail here after checking out the code. I do get your point of having this on backend, but its simply uncessary. Once again thank you for replying yesterday. If you guys require something else, do let me kno. Plus just a small quick reminder tht hacktober fest ends in like 11 days. Thank you