[dpazj]

Summary

Replaces the remaining Result<_, ()> error types with typed errors across the client, app, edge-node, and types crates.

This is a breaking change for the affected public APIs.

Client

• Add an opaque srad_client::ClientError wrapping Box<dyn Error + Send + Sync>.
• Return ClientError from all Client methods.
• Keep DynClient object-safe by using a single concrete error type.
• Map rumqttc errors into ClientError without exposing backend-specific variants.

App

• AppClient publish methods now return ClientError.
• Add BdseqError for missing, invalid, and out-of-range BDSEQ values.
• PayloadError::InvalidBdseq now carries the underlying BdseqError.
• Fix the previously swapped InvalidBdseq / MissingTimestamp messages.

EoN

• Add PublishError::Client and propagate client failures instead of masking them as StateError::Offline.
• node_birth now returns PublishError and logs the actual failure.
• Add MessageMetricError and MessageMetricsError.

Types

• Add DataTypeError, QualityError, PropertyValueError, and PropertySetError.
• PropertySet::insert reports ReservedQuality.
• Add TemplateError::MissingValue and TemplateError::ValueConversion.
• Template derive output now propagates typed conversion errors instead of discarding them.