feat: UX enhancements, member limits, forecast fix, and menu cleanup (v2026.3.19)

- Onboarding wizard: add Reserve Account step between Operating and Assessments,
  redirect to Budget Planning on completion
- Dashboard: health score pending state shows clickable links to set up missing items
- Projects/Vendors: rich empty-state wizard screens with real-world examples and CTAs
- Investment Planning: auto-refresh AI recommendations when empty or stale (>30 days)
- Hide Invoices and Payments menus (see PARKING-LOT.md for re-enablement)
- Send welcome email via Resend when new members are added to a tenant
- Enforce 5-member limit for Starter/Standard/Professional plans (Enterprise unlimited)
- Cash flow forecast: only mark months as "Actual" when journal entries exist,
  fixing the issue where months without data showed as actuals
- Bump version to 2026.3.19

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PARKING-LOT.md

@@ -0,0 +1,22 @@
+# Parking Lot — Features Hidden or Deferred
+
+This document tracks features that have been built but are currently hidden or deferred for future use.
+
+---
+
+## Invoices & Payments (Hidden as of 2026.03.19)
+
+**Status:** Built but hidden from navigation
+
+**What exists:**
+- Full Invoices page at `/invoices` with CRUD, generation, and management
+- Full Payments page at `/payments` with payment tracking and reconciliation
+- Backend API endpoints for both modules are fully functional
+- Routes remain registered in `App.tsx` (accessible via direct URL if needed)
+
+**Where hidden:**
+- `frontend/src/components/layout/Sidebar.tsx` — Navigation links commented out in the Transactions section
+
+**To re-enable:**
+1. Uncomment the Invoices and Payments entries in `Sidebar.tsx` (search for "PARKING-LOT.md")
+2. No other changes needed — routes and backend are intact