Cost calculator and optimization guide

[troyscott]

Description

Provide an accurate, maintained cost breakdown and optimization tips.

Deliverables

• docs/cost-breakdown.md with itemized costs per SKU
• scripts/estimate-cost.sh that queries current Azure pricing
• Tips: auto-pause SQL, B1s for Tailscale VM, reserved instances, etc.

Target costs

• Dev environment: ~$20/mo
• Staging: ~$20/mo (identical, auto-pause)
• Production: ~$50-100/mo (scaled up, no auto-pause)

Acceptance criteria

• Cost doc accurate to within 10%
• Script estimates monthly cost for a given config
• Optimization tips documented