Planespotters 403s server clients whose User-Agent has no contact
email; compose default UA lacked one. Leaflet popup.update() also
re-ran the bindPopup factory and wiped the thumbnail after load.
- Send a contact UA on planespotters lookups; align compose default.
- Resize the popup without re-rendering content.
- Keep hex/src on live firefighter upserts so they get a photo too.
