feat(console): real-mode nav/route gating (hide no-backend screens)

[hitakshiA]

Epic: #58 · Step B (Real-mode nav/route gating) — the last step.

Now that the backend-backed features are wired (auth #60, onboarding #63, treasury #65, payroll #66), make real mode honest: expose only the screens that actually talk to the eERC backend, and keep the full console in demo mode as the product vision. This is a gating/routing change — no new feature work.

Which screens have a real backend (KEEP in real mode)

• Treasury (/treasury) — org-scoped, wired.
• Payroll (/payroll) — run lifecycle, wired.
• Settings & team (/settings) — PARTIAL: keep the org info + team/members (backed by /orgs/:id/members); hide the no-backend cards inside it (integrations, approval policies) in real mode.
• Onboarding is the entry (already gated by RootGate).

No backend → hide in real mode (stay demo-only)

Overview/Dashboard (/), Contractors (/contractors), Invoices (/invoices), Approvals (/approvals), Auditor access / Grants (/grants), Audit log (/audit), and Pay / one-off payment (/pay — the screen whose per-account balance was stubbed in #65; no /payments engine exists). These render from demo stubs only.

Changes

• app/Shell.tsx — the sidebar NavItems are filtered by mode: in real mode (!DEMO_MODE) render only the KEEP set (Treasury, Payroll, Settings); demo mode renders the full set unchanged. Do the same for any command-palette list in app/CommandBar.tsx.
• Routes — in real mode, the hidden screens' routes must not render a broken screen: redirect them to the real-mode default (/treasury). Keep all routes in demo mode. (Find the route table — likely in Shell.tsx or an App/router file — and gate it on DEMO_MODE.)
• Real-mode landing — default/index route resolves to Treasury in real mode (Overview has no backend). Demo keeps Overview as the landing.
• screens/Settings.tsx — in real mode, render only the backed sections (org, team/members); hide the integrations + approval-policy cards. Demo shows all.
• Prefer a single small helper (e.g. an exported REAL_MODE_ROUTES/isRealBackedRoute or a navItems array filtered by DEMO_MODE) over scattering DEMO_MODE checks. Keep it obvious and centralized.

Non-goals

Don't delete the hidden screens or their demo data — they must still work under VITE_DEMO_MODE=1. Don't build a real Overview/dashboard (no backend for it) — just land on Treasury in real mode. No changes to the wired features themselves.

Definition of done

• Real build (pnpm --filter @benzo/console build, no demo flag): nav shows only Treasury / Payroll / Settings; visiting /contractors, /invoices, /approvals, /grants, /audit, /pay, / redirects to /treasury.
• Demo build (VITE_DEMO_MODE=1): full nav + all screens exactly as today.
• Add/extend a test asserting the real-mode nav set and a redirect (e.g. /invoices → /treasury when !DEMO_MODE).
• Gates: typecheck · test · build · VITE_DEMO_MODE=1 build · pnpm exec biome lint . all green.

Operating rules

No git (can't commit). Match the codebase style. End with (1) a one-line conventional-commit message and (2) the exact git add <paths> list.