fix: Critical bugfix for MD5 checksums and R CMD check warnings (v0.5.4)

Merges PR #36: Critical bugfix for Zenodo MD5 checksums + comprehensive validation safeguards

Author: ericscheier

.Rbuildignore

@@ -48,6 +48,7 @@
 ^data/nerc_regions\.gdb/
 ^data/PGE_DIDF_Tables_Public/
 ^data/PGE_POSTSR2A_3-1-2022\.gdb/
+^data/\.archived_bad_data/
 
 # Analysis scripts and outputs (keep in repo but not package)
 ^analysis/