Per RFC 7232:
- Section 3.4: If-Unmodified-Since MUST be ignored when If-Match is
present (If-Match is the more accurate replacement)
- Section 3.3: If-Modified-Since MUST be ignored when If-None-Match is
present (If-None-Match is the more accurate replacement)
Previously, all four conditional headers were evaluated independently.
This caused incorrect 412 responses when If-Match succeeded but
If-Unmodified-Since failed (should return 200 per AWS S3 behavior).
Fix applied to both validateConditionalHeadersForReads (GET/HEAD) and
validateConditionalHeaders (PUT) paths.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
