=== VALID CASES ===
pipeline_2026_sms.pdf => MATCH
upload_123.jpg => MATCH
docreq_456.docx => MATCH
file_name-with-dash.txt => MATCH

=== INVALID CASES (path traversal) ===
../../../etc/passwd => BLOCKED
file..name.pdf => MATCH (PROBLEM!)
..pdf => MATCH (PROBLEM!)
file.pdf. => BLOCKED
.hidden.txt => MATCH (PROBLEM!)

=== DOUBLE-DOT CHECK ===
../file.pdf => strpos('..') = FOUND (blocked)
file..pdf => strpos('..') = FOUND (blocked)