Construction Company Management Web App Development -- 2

We are looking for an experienced developer or small team to build, from scratch, a web-based management system for a construction and building-maintenance company based in Porto, Portugal.

The system covers the full cycle of our business: leads from our website and partners, quote requests (kanban board), scheduling of site visits synced with Google/Microsoft calendars, mobile site surveys with photos and voice notes, quote building with versions and PDF/Excel output, an AI assistant that reads bills of quantities, contracts, project management, payment schedules and referral commissions, plus a client portal.

We currently run a version of this system on a no-code AI platform. The features are proven in daily use, but we need a stable foundation: a relational database, server-side business rules, a full audit trail, automated tests and separate environments. The interface must be in European Portuguese.

A detailed Request for Proposal (scope, business rules, data model, integrations, phases and acceptance criteria) is attached. Please include in your proposal: relevant experience, proposed stack, price and timeline per phase, estimated running costs and your maintenance model.