[M5] verify-curated-db.sh + boost recipe (header-only)

scripts/curated-snippets/abseil-cpp.cpp

@@ -0,0 +1,8 @@
+#include <absl/strings/str_cat.h>
+import std;
+
+int main() {
+    auto s = absl::StrCat("abseil-", "cpp");
+    std::println("abseil-cpp ok: {}", s);
+    return 0;
+}