Cost optimization recommendations and budget gates

[arnaudlh]

Description

The cost estimator skill estimates monthly costs but offers no optimization recommendations or budget thresholds. The manifesto emphasizes cost as a compliance dimension enforced across generation, plan, and deploy phases.

Scope

1. Budget thresholds — Configurable monthly budget in .azure/git-ape.yml. Deployments exceeding the budget require explicit override.
2. Cost optimization recommendations — After estimation, suggest reserved instances, right-sizing, savings plans.
3. Azure Cost Management integration — Query Azure Advisor for cost optimization recommendations on deployed resources.
4. Cost trend tracking — Track cost estimates across deployments over time in state.json.
5. PR cost comparison — When a template changes, show cost delta in the plan PR comment.

Acceptance Criteria

• Budget threshold is configurable.
• Deployments exceeding budget are flagged/blocked.
• Cost optimization suggestions included in estimates.
• Cost deltas shown when templates are modified.
• Historical cost tracking in deployment state.