Dashboard data store - Warn when the context store can't hold a live proxy [2/3]

[n-lark]

Description

The global.dashboard store is a Proxy, behavior, not data, so it can't serialize. On a context store with cache: false there's no in-memory copy, so every read strips the traps and reactivity silently dies.

isInMemoryBacked() probes with a synchronous get and treats a throw as "not in-memory-backed". ui-base injects only when it passes, else node.warns turning a silent failure into a clear warning.

Related Issue(s)

Relates to https://github.com/FlowFuse/engineering/issues/249

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