feat(grafana): migrate Kiro engineering dashboards

[warren830]

Stacked delivery

Depends on #9077. Its full dependency chain is #9075 -> #9076 -> #9077 -> this PR.

This PR is ready for review, but do not merge it until its direct dependency lands. Its clean layer is 12 files, 1,993 additions and 515 deletions.

Summary

• migrate Kiro credits/DORA, AI cost efficiency, multi-AI comparison, steering adoption, language heatmap, and developer-productivity dashboards
• update both MySQL and PostgreSQL variants
• use user model-message rows as the authoritative model distribution source
• retain existing dashboard layout and unrelated configuration

Validation

• all 124 MySQL/PostgreSQL dashboard JSON files parse successfully
• no duplicate Kiro UIDs
• after this layer, Grafana dashboard sources contain zero q_dev runtime references
• final source JSON was provisioned and visually verified against real Kiro collection data

Signed-off-by: warren warren.chen830@gmail.com