Include updatedAt timestamp in MQTTTopicSchema

[hardillb]

part of FlowFuse/mqtt-schema-agent#21

Description

This includes the last update time for a topic so the agent can use it to filter new uploads by only sending changed values.

It also adds a pre-handler to allow the agent token to download the existing topics

Related Issue(s)

FlowFuse/mqtt-schema-agent#21

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 41.66667% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.53%. Comparing base (04e59fe) to head (6b13216).

Files with missing lines	Patch %	Lines
forge/ee/routes/teamBroker/3rdPartyBroker.js	36.36%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7246      +/-   ##
==========================================
- Coverage   76.56%   76.53%   -0.03%     
==========================================
  Files         405      405              
  Lines       20590    20601      +11     
  Branches     4977     4982       +5     
==========================================
+ Hits        15764    15768       +4     
- Misses       4826     4833       +7     

Flag	Coverage Δ
backend	76.53% <41.66%> (-0.03%)	⬇️

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