fix(watcher): skip context when Microcks client cannot be created

[SAY-5]

Problem

In TriggerImport, when connectors.NewClient fails it logs the error but
keeps going, so the code reaches mc.UploadArtifact with a nil client and the
watcher process panics with a nil pointer dereference (#475). This happens for
example when a watch entry references a context that cannot be resolved.

Fix

continue to the next context after logging the connection error, so a failed
context is skipped instead of crashing the daemon.

Added a regression test in pkg/watcher that drives TriggerImport with an
unresolvable context; it panics without the change and passes with it.

Fixes #475