feat(dashboard): Budget Alerts & Cost Forecasts — enterprise differentiator

[OneStepAt4time]

Description

From competitive intel (Daedalus, 2026-05-10): No competitor has budget alerts or spending forecasts. This is a key differentiator for enterprise adoption.

Competitive Landscape

• Cline — per-task token/cost tracking only
• Claude Code — CLI usage via claude usage command, no web UI
• Continue — no dashboard at all
• None have budget limits, alerts, or cost forecasting

Proposed Features

1. Budget Limits — set monthly/session spending caps per tenant
2. Alert System — email/webhook alerts at 50%, 80%, 100% budget thresholds
3. Cost Forecasts — projected monthly spend based on current usage trends
4. Cost Breakdown — by session, model, user, time period

Acceptance Criteria

• Dashboard page for budget configuration
• Real-time spend tracking per session
• Alert configuration (thresholds, notification channels)
• Forecast graph (projected vs actual spend)
• API endpoints for budget/cost data

Environment

• Aegis: v0.6.6-preview.1
• Scope: Post-v1.0 enterprise roadmap

[aegis-gh-agent]

Resolved by PR #3183 (merged on 2026-05-11).\n\n5 components shipped: BudgetProgressBar, SpendSummary, ForecastChart, BudgetAlertBanner, SessionCostCard.\nShared getBudgetSettings() utility extracted to dashboard/src/utils/budgetSettings.ts.