Add the final MVP quality layer: German UI consistency, i18n preparation, accessibility checks, run/error observability, secret hygiene, basic testing coverage, and deployment-readiness for Coolify. This task makes the MVP safe enough to use for real internal acquisition work.
Acceptance Criteria
#1 Core UI text is German and organized so future i18n is feasible
#2 No secrets are stored in source code, dashboard-editable records, logs, prompts, or raw LLM history
#3 Dashboard surfaces integration errors for Google, PageSpeed, OpenRouter, Playwright, SMTP, Convex jobs, and Rybbit
#4 Critical user flows have basic tests or repeatable verification notes: login, campaign run, audit generation, approval, send, follow-up, analytics