Fix intrange and G101 linting issues

- Convert for loops to use Go 1.22+ integer ranges in generate.go and helpers.go
- Disable G101 false positives for test vectors and environment variable names
- Add file-level gosec disable for bip85_test.go containing BIP85 test vectors
- Add targeted nolint comments for legitimate test data and constants

pkg/bip85/bip85_test.go

@@ -1,6 +1,7 @@
+//nolint:gosec // G101: Test file contains BIP85 test vectors, not real credentials
 package bip85
 
-//nolint:gosec,revive,unparam // Test file with hardcoded test vectors
+//nolint:revive,unparam // Test file with BIP85 test vectors
 
 import (
 	"bytes"