fix: detecting diff error swallowing

[andreabadesso]

Motivation

The wallet-service-daemon got stuck in the detectingDiff state for 12+ hours on testnet-india (2025-12-15). Root cause analysis revealed that xstate silently swallows errors from invoked services when no onError handler is defined, and this behavior produces no logs in production mode (NODE_ENV=production). The metadataDiff invoke was the only one missing an onError handler.

Additionally, getDbConnection() was outside the try/catch block.

Acceptance Criteria

• Add onError handler to detectingDiff invoke so errors transition to ERROR state instead of being silently swallowed
• Move getDbConnection() inside try/catch in metadataDiff so connection errors are properly logged
• Audit all other invoke states - confirmed all others already have onError handlers

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged
• Make sure either the unit tests and/or the QA tests are capable of testing the new features
• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

The base branch was changed.