feat(grafana): add core Kiro dashboards

[warren830]

Stacked delivery

Depends on #9076, which depends on #9075. Merge in that order; this PR is ready for review but must not merge until its direct dependency lands.

After the preceding PRs merge, GitHub will reduce this PR to its own 14-file layer: 1,348 additions and 990 deletions.

Summary

• migrate the MySQL/PostgreSQL Kiro DORA, activity detail, executive, feature-metrics, logging, and user-report dashboards
• preserve panel IDs, layout, datasources, variables, and visualization settings
• use Kiro report/model-message/chat/completion tables without fabricating acceptance metrics
• keep MySQL and PostgreSQL variants on unique UIDs

Validation

• all dashboard JSON files parse successfully
• Kiro dashboard UIDs have no conflicts
• source queries were previously validated against real MySQL collection data and isolated Grafana provisioning

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