DEV - Update cashflow chart with live cost and revenue data, add custom cost/revenue interval #412

Overview

We are updating the cash flow chart to reflect real cost and revenue data. Also adding an option to allow the user to enter custom month intervals for costs and revenues (eg. quarterly), where users should be able to select a starting date, and then how often the cost repeats from that starting date.

Tasks

• Add an option to Cost and Revenue card on Cashflow page for user to select a custom frequency in months. Would probably be easiest to have this not be an enum but just a number of months
• Add field for user to input Start Date
• Wire cost and revenue data from app state into the chart component
• Ensure the chart re-renders when cost or revenue records are added, edited, or deleted
• Validate axis labels, legend labels, and projection logic
• Handle empty state (no cost or revenue data)
• QA the chart across different data volumes and date ranges

Acceptance criteria

• Chart renders with actual cost and revenue data from app state.
• Chart updates reactively when cost or revenue records change.
• The custom frequency option adds the cost or revenue in the correct amount of monthly intervals starting from the user’s inputted start date.