Liu - Develop a Google Appsheet Project Management Application with Google Sheets Backend

A freelancer is needed to develop a comprehensive Project Management application using Google AppSheet, with Google Sheets serving as the backend database. This application is designed to streamline workflows for a services/engineering-style business.

The core functionality requires configurable lists for various project attributes such as types, statuses, and priorities. These configurations must be managed through reference tables within Google Sheets, ensuring flexibility and ease of updates without hardcoding.

Key requirements for the application include:

*  **Backend Integration**: The AppSheet application must be connected to a robust Google Sheet schema. This schema will include essential tables such as Projects, Organizations, Contacts, Engineers, ProjectTasks, ProjectEngineers, Templates, TemplateTasks, ActivityLog, Notifications, and MonthlySequences.
*  **Configurable Enums**: Implement configurable enum tables for Project Types, Project Statuses, Priorities, Payment Statuses, Task Types, and Organization Types. Each enum table must include an 'Active' flag to control the visibility and selection of values, ensuring only active options are available.
*  **Project Details**: Each project record must encompass critical information including project type, status, priority, and payment status (all linked via reference tables). It should also track due dates, incorporate overdue logic, and manage financial fields such as estimated budget, actual cost, and invoice amount. Address/location details and a notes section are also required.
*  **Data Relationships**: Establish the following relationships within the application:
    *  Organizations to Contacts (one-to-many)
    *  Projects to Engineers (many-to-many)
    *  Projects to Tasks (many-to-many, including completion tracking)
    *  Templates to Template Tasks
*  **User Views and Features**: The application must provide several intuitive views and functionalities:
    *  A clear Project list and detailed Project view.
    *  A Dashboard displaying summary counts and charts for key metrics.
    *  A Calendar view to visualize projects based on their creation and/or due dates.
    *  An Engineer workload view to monitor assignments.
    *  A Client/Organization overview for quick access to related information.
    *  An Audit trail, utilizing the ActivityLog table, to record significant project changes (e.g., Status updates, payment status changes, engineer assignments).
    *  A Notifications view to alert users about upcoming deadlines, overdue projects, and overdue invoices. This can be driven by table data or computed logic.
*  **Project Numbering**: Implement a custom project numbering system following the format hf-yymm###, with the sequential number resetting monthly. A reliable approach using AppSheet automation or a Google Apps Script endpoint is preferred for this functionality.