hotfix: resolve tenant data leak, DB pool, and cent rounding

[ramazanberkozbek]

• Fixed DatabasePool asyncpg configuration and removed the silent fallback to fake mock data ($1000). Real database errors now fail closed instead of hiding behind hardcoded numbers.
• Fixed cross tenant data leak by scoping the Redis cache key with tenant ID (revenue:{tenant_id}:{property_id}). Tenants sharing property IDs like prop-001 no longer see each other's cached revenue.
• Fixed cent rounding discrepancies by summing revenue with Python Decimal and ROUND_HALF_UP instead of float.
• Accounted for property timezone (Europe/Paris) on check-in dates so Sunset's March total correctly includes the 29 Feb 23:30 UTC booking ($2250.00 across 4 bookings).
• Removed the timestamp in RevenueSummary.tsx to let client side caching work properly.

Tested

• sunset@propertyflow.com: Beach House Alpha shows 2250.00 and 4 bookings.
• ocean@propertyflow.com: Mountain Lodge Beta (prop-001) shows 0.00 on refresh (no cross tenant bleed). Lakeside Cottage shows 1776.50 and 4 bookings.