feat: parse and display security info (M3)

Implement security info parsing including RSA signature, encrypted AES
key, image/region/media flags, load address, SHA-1 digests, and page
descriptors with section type classification. Add comprehensive unit
and integration tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main.rs

@@ -27,4 +27,5 @@ fn main() {
 
     xex2tractor::display::display_header(&xex.header);
     xex2tractor::display::display_optional_headers(&xex.optional_headers);
+    xex2tractor::display::display_security_info(&xex.security_info);
 }