Add spend insights and group budgets

[asizikov]

Summary

This PR helps report viewers understand why usage-based billing spend is concentrated and who is driving it. It adds Spend Insights for AIC gross cost concentration and uses those spend groups to suggest and simulate user-level budgets.

Fixes #101

Changes

Commit	Change
feat: classify users by AIC gross spend	Persists each user's AIC gross spend group after aggregation and adds reusable spend segmentation helpers/tests.
feat: add spend insights view	Adds a Spend Insights page with concentration metrics, top spend drivers, and spending by group.
feat: add spend group budget controls	Adds Universal, Heavy, and Power user-level budget controls, prepopulates them from group averages, and applies group-specific overrides in budget simulation.
fix: address spend insights review feedback	Fixes blank segment budgets falling back to the universal budget, hides Spend Insights for single-user reports, and bases top 10% concentration on users with AIC gross cost.

Additional notes:

• Spend Insights is hidden for individual and other single-user reports because percentile groups are not meaningful for one user.
• Budget controls use AIC gross cost for per-user caps and additional AIC spend for account/product caps.

Testing

• npm run lint
• npm test
• npm run build

Checklist

• Specs lint passes (npm run lint)
• Tests updated if applicable
• Documentation updated if applicable

[Copilot]

Pull request overview

This PR adds user spend segmentation for AIC gross cost, exposes a Spend Insights view, and uses those segments to prepopulate and apply group-specific budget simulations.

Changes:

• Classifies users into spend groups and adds spend insight calculations/tests.
• Adds a Spend Insights page and user detail spend group labels.
• Adds group budget defaults and applies Heavy/Power budget overrides during simulation.

Show a summary per file

File	Description
src/App.tsx	Wires Spend Insights navigation/view and budget default/simulation state.
src/views/UserDetailsView.tsx	Displays a user’s spend group.
src/views/SpendInsightsView.tsx	Adds the Spend Insights UI.
src/views/CostManagementView.tsx	Adds group-specific budget controls.
src/pipeline/aggregators/userUsageAggregator.ts	Persists spend segment per aggregated user.
src/utils/userSpendSegments.ts	Adds segmentation and concentration helpers.
src/utils/userSpendSegments.test.ts	Tests spend insight helpers.
src/utils/costManagementBudgets.ts	Adds budget value helpers/defaults.
src/utils/costManagementBudgets.test.ts	Tests budget helper defaults/lookups.
src/utils/budgetSimulation.ts	Applies segment-specific user budget caps.
src/utils/budgetSimulation.test.ts	Tests segment budget simulation behavior.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

• Files reviewed: 11/11 changed files
• Comments generated: 3