## Context
Fixes the following 2 issues with the database selection in the SQL
Editor
- An errant `useEffect` was resetting the `selectedDatabaseId` back to
the primary every time the `databases` list from `useReadReplicasQuery`
changed reference (not just on first load).
- `QuerySourceMenu` kept showing "Read Replica" even after selection had
reverted
- Was using local storage value as the `identifier` for
`DatabaseParametersSubMenu`, when it should use the valtio store as the
source of truth
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **Improvements**
- The SQL Editor now remembers the last selected database between
sessions.
- Your saved database selection is restored when available; otherwise,
the project’s primary database is selected automatically.
- Query source settings now stay synchronized with the database
currently selected in the SQL Editor.
- **Bug Fixes**
- Background database refreshes no longer unexpectedly reset your
selected read replica to the primary database.
- Database selection now waits for saved preferences to load, preventing
a brief incorrect selection.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
