Aggregate /trends, /top-recurring, /category-trend by report_date instead of
per-upload row. Add sibling-upload disclosure to /summary. Filter persistUpload
snapshot query by the upload's vertical to prevent cross-vertical contamination.
Fixes GitLab #12 (reported by nkapur — STEAM active findings chart showed 3
entries for 5/11 after uploading three vertical data sets for that date).
Includes 30 property-based tests covering bug condition and preservation.
