security: update gitignore with sensitive file patterns

Add .env.*, *.key, *.pem, api_keys, .secure/, *.secret,
.git-credentials to prevent accidental secret commits.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -4,5 +4,12 @@ evidence/
 court_data/
 *.pdf
 .env
+.env.*
 test_sandbox/
 *.odt
+*.key
+*.pem
+*.secret
+api_keys
+.secure/
+.git-credentials