Fix all build/type/lint errors (zod 3.25 compat wrapper, Svelte 5 fixes),
write 115 unit tests across 10 test files, expand seed script with demo
data, update Docker config with migration on startup.
Add admin layout with auth guard, user management (CRUD + group membership),
group management, system settings (auth mode, registration, theme, healthcheck),
permission editor component, and global search API endpoint.
alexei.dolgolyov