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>

.gitignore

@@ -0,0 +1,32 @@
+# --- RStudio & System Basics ---
+.Rproj.user
+.Rhistory
+.RData
+.Ruserdata
+.DS_Store
+
+# --- SECURITY: Never commit these ---
+.Renviron
+.Rprofile
+*.secret
+credentials/
+
+# --- DATA: The "Lake" Rule ---
+# Since data lives on Smaug/MinIO, we ignore any local data attempts
+data/*
+!data/README.md
+*.csv
+*.parquet
+*.rds
+
+# --- WORKFLOW: Targets (for when you switch later) ---
+_targets/
+_targets.user/data/
+.Renviron
+
+/.quarto/
+**/*.quarto_ipynb
+docs
+
+/dev/
+/scratch/