feat: GPU Hour Calculator (M116)

[hlin99]

Summary

Add GPU Hour Calculator (M116) — given benchmark data and a daily traffic profile (hourly QPS schedule), estimate total GPU hours, costs, and auto-scaling savings.

Changes

• GPUHourCalculator class in gpu_hours.py with QPS-to-instance mapping
• TrafficProfile, HourlyTraffic, GPUHourReport, ScalingSavings, HourBreakdown Pydantic models
• 24-hour traffic profile input with per-hour QPS values
• Auto-scaling savings: compare fixed (peak) vs dynamic (per-hour) provisioning
• CLI gpu-hours subcommand with --benchmark, --traffic-profile, --gpu-cost, Rich table + JSON output
• Programmatic calculate_gpu_hours() API
• 24 new tests covering models, calculator, CLI, edge cases, public imports
• Updated ROADMAP.md (M115 ✅, M116 🔄) and docs/iterations/current.md

Closes #255

[hlin99-Review-Bot]

✅ Approved (hlin99-Review-Bot)

CI all green (lint + tests 3.10/3.11/3.12). Code review:

• Idea: GPU Hour Calculator fits naturally as M116 — practical cost estimation from traffic profiles with auto-scaling savings analysis. Good addition.
• Code quality: Clean Pydantic models with proper validation (hour range, unique hours, sorted output). Calculator logic is straightforward and correct. CLI well-structured with Rich table + JSON output.
• Tests: 24 tests covering models, calculator, CLI, edge cases, and public imports. Good coverage.
• Docs: ROADMAP.md and iterations/current.md updated correctly.

Ship it.

[hlin99-Review-BotX]

✅ Approved (hlin99-Review-BotX)

CI all green (lint + tests 3.10/3.11/3.12). Code review:

• Idea: GPU Hour Calculator is a natural M116 addition — maps traffic profiles to GPU cost estimates with auto-scaling savings analysis. Practical and well-scoped.
• Code quality: Clean Pydantic models with proper validation (hour range 0-23, unique hours, sorted output). Calculator logic is straightforward — QPS-to-instance mapping with ceil, fixed vs dynamic comparison. CLI follows established patterns (Rich table + JSON).
• Tests: 24 tests covering models, calculator, CLI, edge cases, and public imports. Good coverage.
• Docs: ROADMAP.md (M115 ✅, M116 🔄) and iterations/current.md updated correctly.

Ship it.