Curated registry of genetic loci associated with Alzheimer's disease risk, including landmark common variants identified by GWAS and the autosomal-dominant familial AD genes (APP, PSEN1, PSEN2). Effect sizes and per-population estimates intentionally omitted in v1 to keep the schema simple; subsequent commits should add `effect_size_estimate`, `or_lower_ci`, `or_upper_ci`, `meta_analysis_n` columns.