chore: Posts page translations (en/de)

[arturasmckwcz]

Context

Translation pass for every new label/string introduced across the Posts page rebuild sub-issues (composer, feed, post card, replies, reactions, bookmark, search/people widget).

Scope

• Add en + de entries to public/locales/{en,de}/translations.json for all new UI copy
• Do this incrementally as each sub-issue lands rather than all at once at the end, to avoid a last-minute pile-up — this issue tracks the final audit pass to catch anything missed

Acceptance criteria

• No hardcoded English strings remain in any Posts-page component
• en and de translation files have matching keys for all Posts-page copy

Part of Epic: #969