Remove magic byte detection in favor of simple UTF-8 validation:
- text/plain for valid UTF-8 content
- application/octet-stream for binary data
Security maintained via headers (X-Content-Type-Options: nosniff, CSP).
Magic signatures preserved as comments for future reference.
Disabled test files:
- test_mime_detection.py.disabled (magic-dependent tests)
- test_polyglot.py.disabled (polyglot format tests)
For full MIME detection, consider using the `filetype` library.
- test_magic_prefix_detection: verify all signatures with random suffix
- test_random_binary_never_crashes: random data never crashes
- test_partial_magic_no_false_match: truncated magic handled safely
- test_magic_not_at_start_ignored: only detect magic at offset 0
