GPX files containing both <wpt> and <trk> elements would only import
waypoints, silently discarding track geometry. The fallback chain only
parsed <trkpt> when no waypoints were found.
Replaced all regex-based XML parsing helpers with fast-xml-parser for
correctness (namespaces, CDATA, attribute ordering). Tracks are now
always parsed independently of waypoints, with each <trk> element
becoming its own place with route geometry. Fixes#427.