chore: gitignore /private/ folder

Holds local-only credentials, forensic captures, and per-server creds
files that must never be committed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -51,5 +51,8 @@ docker-compose.override.yml
 # Filesystem storage backend root (FilesystemBackend default location)
 /storage/
 
+# Private credentials + forensic captures — never commit
+/private/
+
 # Local berth-PDF + brochure samples used as upload fixtures during dev.
 /berth_pdf_example/