feat(l10n): add Spanish translations

Translate all 253 user-facing strings to Spanish (formal "usted"), including
the transfer_file_count plural. Generates values-es/strings.xml for KMP, es
localizations in the Apple catalog, and adds es to CFBundleLocalizations.

apple/VniDrop/Resources/Info.plist

@@ -6,6 +6,7 @@
 	<array>
 		<string>en</string>
 		<string>fr</string>
+		<string>es</string>
 	</array>
 	<key>CADisableMinimumFrameDurationOnPhone</key>
 	<true/>