Create the database table and model for storing pre-calculated verification state counts for CI job artifacts. This table uses a bucketed approach where rows are distributed across 100k buckets via modulo (`job_artifact_id % 100_000`). Each bucket stores aggregated counts (total, verified, failed) that can be summed instantly instead of scanning the entire `ci_job_artifact_states` table. **Changes:** - Migration to create `geo_ci_job_artifact_verification_summaries` table on CI database - `Geo::CiJobArtifactVerificationSummary` model - Factory and model specs - Database dictionary entry **Part of:** #512646