feat: add i18n descriptions to all hands and channels (#22)

Add [i18n.zh], [i18n.zh-TW], [i18n.ja], [i18n.ko], [i18n.de], [i18n.es]
sections with translated descriptions to:
- 15 Hand TOML files (hands/*/HAND.toml)
- 44 Channel TOML files (channels/*.toml)

This enables the website to display localized Hand and Channel descriptions
based on the user's selected language.

channels/threema.toml

@@ -5,6 +5,24 @@ category = "messaging"
 icon = "🔏"
 protocol = "rest-api"
 
+[i18n.zh]
+description = "Threema Gateway 适配器，通过 Threema 平台进行安全通信"
+
+[i18n.zh-TW]
+description = "Threema Gateway 適配器，透過 Threema 平台進行安全通訊"
+
+[i18n.ja]
+description = "Threema Gatewayアダプター、Threemaプラットフォームによるセキュアメッセージング"
+
+[i18n.ko]
+description = "Threema Gateway 어댑터, Threema 플랫폼을 통한 보안 메시지 송수신"
+
+[i18n.de]
+description = "Threema Gateway-Adapter für sichere Nachrichten über die Threema-Plattform"
+
+[i18n.es]
+description = "Adaptador de Threema Gateway para mensajería segura a través de la plataforma Threema"
+
 [metadata]
 url = "https://threema.ch"
 docs = "https://gateway.threema.ch/en/developer/api"