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/services/label_sheet_service.dart

@@ -36,7 +36,7 @@ class LabelSheetLabel {
   /// The batch facts line ("2006 · Perales · 2 cobs"), if any.
   final String? details;
 
-  /// The QR payload (a `tanemaki://seed` URI), so the seed's data rides on the
+  /// The QR payload (a `tane://seed` URI), so the seed's data rides on the
   /// physical packet.
   final String qrData;
 }