Unscoped GET /auth/feishu is disabled by default. Derive org slug from
/admin/org/:slug, ?org=, or the Alpha Silo hostname and redirect to
/auth/feishu/:orgSlug so the login button works on tenant domains.
Run `prettier --write .` across all source files. Changes are purely
formatting: trailing commas, line wrapping at 120 chars, import
reordering, and CSS whitespace. No logic changes. Verified with
`prettier --check .` and `svelte-check` (0 errors, 0 warnings).