Design an offline action queue with visible conflicts

For [USER ACTIONS], [SYNC API] and [CONFLICT RULES], design an offline queue that survives reload, preserves order where required and prevents duplicate effects on retry. Specify local state, server acknowledgements, idempotency keys, conflict UI and tests for network drop at each stage. Do not silently overwrite another user's newer change. Provide a minimal implementation outline and a state transition table. Check that a user can see pending, failed and resolved actions and that deleting local data is never the default recovery step.