Add German language selection and persisted locale support, complete German
label and format catalogs, and German release notes. Connect previously
untranslated UI text, preserve user names, and size translated buttons to
fit. Format cached import source facts in the active UI language.
Validate locale coverage, placeholder formats, language persistence,
German glyphs, button bounds and cached import language switching. Review
native and headless screenshots; run all seven cargo xtask ci gates.
Co-Authored-By: Codex (GPT-6) <[email protected]>
