Builds a real pre-designs database (nodes/edges without design_id, integer
canvas_state PK) and asserts init_db() adopts everything into a single
default Network Topology design with the viewport preserved, and that the
migration is idempotent across reboots. The rest of the suite uses create_all
and never exercised this in-place upgrade path.
ha-relevant: yes
Pouzor
4ce8a12720