refactor(branding): rename app Tanemaki → Tane

Public name is now Tane (種, "seed"); Tanemaki (種まき, "to scatter seeds")
is kept only as etymology in the About screen and onboarding.

App not yet distributed, so format tokens rename cleanly with no migration:
backup extension .tanemaki→.tane, QR scheme tanemaki://→tane://, file
prefixes tane-*. Website link and species-catalog User-Agent →
tane.comunes.org. Android label capitalised to "Tane".

Identity/crypto constants already use org.comunes.tane (derivation, HKDF
backup, sync namespace, TANE1 recovery tag) — left untouched, so keys,
backups and sync are unaffected. Tests updated; analyze + full suite green.

apps/app_seeds/lib/ui/label_print_sheet.dart

@@ -170,7 +170,7 @@ class _LabelPrintSheetState extends State<_LabelPrintSheet> {
     final saved = await getIt<LabelSheetService>().saveLabels(
       labels: labels,
       format: _format,
-      suggestedName: 'tanemaki-labels-${_today()}.pdf',
+      suggestedName: 'tane-labels-${_today()}.pdf',
       rtl: rtl,
     );