Add Deutsch across all card surfaces and backend flows, backed by the language registry introduced in #62. German loads as a fingerprint-checked page-shared locale chunk so EN/RU remain synchronous and the initial View budget stays intact. Root render gates prevent mixed-language flashes, retry once, and fail open to English. Extend parity, runtime, bundle, browser and visual coverage, plus contributor and user documentation.
Issue: #348
User-Visible: yes
Matysh