chore(local): add S3 migration and CRAN-source helper scripts

- migrate-s3-hetzner-to-backblaze.sh: rclone-based bucket migration helper.
- find-R-api-packages.sh: scan CRAN package sources for a C-API usage pattern.
- query-pkgs-without-old-versions.R, test-package-loading.R: ad-hoc helpers.

local/query-pkgs-without-old-versions.R

@@ -0,0 +1,39 @@
+library(s3fs)
+
+# List all files under contrib/<pkg>/
+all_files <- s3fs::s3_dir_ls(
+  "s3://devxy-r-package-binaries-hel1/arm64/alpine322/latest/src/contrib/",
+  recurse = TRUE,
+  type = "file"
+)
+
+pattern <- ".*/src/contrib/([^/_]+)_.*"
+matches <- regmatches(all_files, regexec(pattern, all_files))
+pkg_names <- unique(
+  vapply(
+    matches,
+    function(x) if (length(x) > 1) x[2] else NA_character_,
+    character(1)
+  )
+)
+pkg_names <- pkg_names[!is.na(pkg_names)]
+
+# For each package, check if Archive/<pkg>/ contains any files
+no_archive_files <- character(0)
+for (pkg in pkg_names) {
+  archive_dir1 <- sprintf(
+    "s3://devxy-r-package-binaries-hel1/arm64/alpine322/latest/src/contrib/Archive/%s",
+    pkg
+  )
+  archive_files <- unique(c(
+    tryCatch(
+      s3fs::s3_dir_ls(archive_dir1, recurse = TRUE),
+      error = function(e) character(0)
+    )
+  ))
+  if (length(archive_files) == 0) {
+    no_archive_files <- c(no_archive_files, pkg)
+  }
+}
+
+print(no_archive_files)