The previous parser read `data.routes` which is just an echo of the
`routes` request flag (a boolean). On real brokers this caused
`TypeError: 'bool' object is not iterable` and 500s during /import.
- Rewrite parse_networkmap to read data.value.nodes + data.value.links
with fallback to data.{nodes,links} for legacy variants
- Defensive: drop links to unknown nodes, propagate lqi from link to
target node, extract model/vendor from definition block
- Bump networkmap timeout 10s -> 180s (large meshes are slow)
- Tests: rewrite fixture builders + sample payload to real Z2M shape;
add cases for legacy shape, routes:false echo (regression), malformed
list, link to unknown node, lqi propagation, definition extraction
- Update docs to mention 60s+ wait window
53 backend tests pass, mypy + ruff clean.