i18n: translate missing amethyst strings for cs, de, sv and pt-BR

Fills the on-disk gaps in the four target locales: channel archive/unarchive,
the new-forum title, the External Content screen title, the archived channel
section header, the three share targets (picture / short / video) and the URL
preview's open-in-browser action.

Wording follows each locale's existing siblings rather than being translated
fresh -- url_preview_open_in_browser reuses the string already in
git_repo_open_in_browser, share_target_as_picture follows new_picture, and
share_target_as_short_video follows home_content_type_shorts.
relay_group_section_archived heads a channel list, so cs/sv/pt take the plural
adjective.

Keys whose translation would be byte-identical to the English source are left
out on purpose: Crowdin strips source-identical entries on export and Android
already falls back to values/strings.xml at runtime. That covers the "workflow"
loanword in cs/de, and Highlights / Podcasts / Reposts / Torrents / Videos /
Name / Backlog in de, plus Podcasts / Torrents / Backlog in pt-BR.

The commons composeResources tree was already complete for all four locales.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WopdqNoZ9tYoMNppJG17BL

amethyst/src/main/res/values-cs/strings.xml

@@ -4792,4 +4792,13 @@
     <string name="buzz_persona_avatar">URL avataru (volitelné)</string>
     <string name="buzz_persona_publishing">Publikování…</string>
     <string name="buzz_persona_publish">Publikovat personu</string>
+    <string name="buzz_channel_archive">Archivovat kanál</string>
+    <string name="buzz_channel_unarchive">Zrušit archivaci kanálu</string>
+    <string name="buzz_forum_create_title">Nové fórum</string>
+    <string name="external_content_title">Externí obsah</string>
+    <string name="relay_group_section_archived">Archivované</string>
+    <string name="share_target_as_picture">Nový obrázek</string>
+    <string name="share_target_as_short_video">Nové krátké video</string>
+    <string name="share_target_as_video">Nové video</string>
+    <string name="url_preview_open_in_browser">Otevřít v prohlížeči</string>
 </resources>

amethyst/src/main/res/values-de-rDE/strings.xml

@@ -4616,4 +4616,13 @@
     <string name="buzz_persona_avatar">Avatar-URL (optional)</string>
     <string name="buzz_persona_publishing">Wird veröffentlicht…</string>
     <string name="buzz_persona_publish">Persona veröffentlichen</string>
+    <string name="buzz_channel_archive">Kanal archivieren</string>
+    <string name="buzz_channel_unarchive">Kanal aus dem Archiv nehmen</string>
+    <string name="buzz_forum_create_title">Neues Forum</string>
+    <string name="external_content_title">Externe Inhalte</string>
+    <string name="relay_group_section_archived">Archiviert</string>
+    <string name="share_target_as_picture">Neues Bild</string>
+    <string name="share_target_as_short_video">Neuer Kurzfilm</string>
+    <string name="share_target_as_video">Neues Video</string>
+    <string name="url_preview_open_in_browser">Im Browser öffnen</string>
 </resources>

amethyst/src/main/res/values-pt-rBR/strings.xml

@@ -4621,4 +4621,13 @@
     <string name="buzz_persona_avatar">URL do avatar (opcional)</string>
     <string name="buzz_persona_publishing">Publicando…</string>
     <string name="buzz_persona_publish">Publicar persona</string>
+    <string name="buzz_channel_archive">Arquivar canal</string>
+    <string name="buzz_channel_unarchive">Desarquivar canal</string>
+    <string name="buzz_forum_create_title">Novo fórum</string>
+    <string name="external_content_title">Conteúdo externo</string>
+    <string name="relay_group_section_archived">Arquivados</string>
+    <string name="share_target_as_picture">Nova Foto</string>
+    <string name="share_target_as_short_video">Novo Vídeo Curto</string>
+    <string name="share_target_as_video">Novo Vídeo</string>
+    <string name="url_preview_open_in_browser">Abrir no navegador</string>
 </resources>

amethyst/src/main/res/values-sv-rSE/strings.xml

@@ -4624,4 +4624,13 @@
     <string name="buzz_persona_avatar">Avatar-URL (valfritt)</string>
     <string name="buzz_persona_publishing">Publicerar…</string>
     <string name="buzz_persona_publish">Publicera persona</string>
+    <string name="buzz_channel_archive">Arkivera kanal</string>
+    <string name="buzz_channel_unarchive">Avarkivera kanal</string>
+    <string name="buzz_forum_create_title">Nytt forum</string>
+    <string name="external_content_title">Externt innehåll</string>
+    <string name="relay_group_section_archived">Arkiverade</string>
+    <string name="share_target_as_picture">Ny bild</string>
+    <string name="share_target_as_short_video">Ny kortfilm</string>
+    <string name="share_target_as_video">Ny video</string>
+    <string name="url_preview_open_in_browser">Öppna i webbläsare</string>
 </resources>