category-trend-analyzer

For each spending category, computes current-period spend, 6-month rolling average, year-over-year delta, and budget variance, then flags categories that are outliers (>1.5x rolling average or >130% of budget). Produces a ranked list of categories that grew, shrank, or stayed flat, plus the top transactions driving each outlier. Use for monthly spending reviews, identifying lifestyle creep, evaluating budget adherence, or when user mentions category trends, spending changes, budget variance, or outlier spend.