Initial commit: BAF Lakehouse fraud detection pipeline

End-to-end LightGBM fraud detection pipeline built as an R package,
orchestrated by targets with data stored in MinIO via Apache Arrow.
Includes 6-layer Lakehouse architecture, class imbalance tournament,
formally tuned hyperparameters (PR-AUC 0.198), and Quarto RevealJS slides.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.Rbuildignore

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+^.*\.Rproj$
+^\.Rhistory$
+^\.RData$
+^\.Renviron$
+^\.Rprofile$
+^Rprofile$
+
+^renv$
+^renv\.lock$
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+^\.git$
+^\.github$
+
+^_targets$
+^_targets\.R$
+
+^reports$
+
+^index\.qmd$
+^_quarto\.yml$
+^\.quarto$
+
+^README\.Rmd$
+
+^LICENSE\.md$
+^scratch$
+^TODO\.md$
+^dev$
+
+^_pkgdown\.yml$
+^docs$
+^pkgdown$