v0.6.6: Fix message keys, reset partition, clear pending

Remove unstable index suffix from MessageRow keys in Kafka and Rabbit consumer views to avoid duplicate/unstable keys. Add a useEffect in MessagesTab to reset the selected partition when the topic changes (prevents out-of-range fetches when switching to a topic with fewer partitions). Ensure discardPending is called when a Kafka consumer start fails so any messages that arrived during the failed start are cleared. A binary change was made to the Rabbit consumer store as part of related fixes.