fix(dashboard): enforce tenant-scoped dashboard access and secure monthly summaries

[etharrra]

This change hardens the dashboard flow across the backend and frontend by enforcing tenant-aware access controls and improving data consistency for property and revenue queries.

Backend updates:

• tighten tenant resolution and property access checks to prevent cross-tenant data leakage
• scope dashboard property listings and summary queries to the active tenant
• ensure monthly revenue aggregation respects local month boundaries and property ownership
• validate single-currency totals for property-level reservation summaries
• clear and refresh tenant-scoped cache entries when dashboard data changes
• add integration coverage for property scoping, month-boundary logic, and cross-tenant access rejection

Frontend updates:

• load dashboard properties dynamically from the authenticated API instead of relying on static mock data
• add a month selector and default-to-latest-month behavior
• pass the selected month through the summary component for accurate revenue filtering
• show user-facing errors when the dashboard data cannot be loaded

Tests:

• add end-to-end integration checks for seeded tenant data, cross-tenant isolation, and summary correctness across multiple months

This keeps the dashboard aligned with the tenant model, prevents unauthorized data access, and verifies the behavior with real API-level regression tests.