[7324] Replace HTTP polling of instance / device status with MQTT-over-WS

[n-lark]

Description

See test plan: #7324 (comment)
See details: #7324 (comment)

Related Issue(s)

Resolves #7324

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 FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

❌ Patch coverage is 95.06173% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.07%. Comparing base (01e79e2) to head (6ba8c73).

Files with missing lines	Patch %	Lines
forge/comms/aclManager.js	86.66%	2 Missing ⚠️
forge/db/controllers/Project.js	97.29%	1 Missing ⚠️
forge/routes/api/projectActions.js	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7573      +/-   ##
==========================================
+ Coverage   76.95%   77.07%   +0.11%     
==========================================
  Files         411      411              
  Lines       21094    21170      +76     
  Branches     5141     5161      +20     
==========================================
+ Hits        16233    16316      +83     
+ Misses       4861     4854       -7     

Flag	Coverage Δ
backend	77.07% <95.06%> (+0.11%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[n-lark]

So devices already publish their raw status to the …/status topics, which forge subscribes to in order to collect it.

If forge re-published the browser-facing copy onto that same …/status topic, it would receive its own message back and loop forever, so the browser updates use a separate …/state topic that nothing on the backend listens to.

Also named instances .../state for consistency. I was also considering .../liveStatus to imply FE, not sold on the name.