Previously FileService fell back to extension-based MIME detection, causing
TIFF, HEIC, DOCX and other unlisted types to be served as octet-stream
(forced download instead of inline display).
- Add content_type column to documents (V3 migration)
- Store file.getContentType() in DocumentService on upload and file replace
- MassImportService uses Files.probeContentType() for local files
- DocumentController prefers doc.getContentType() over S3-reported type
- FileService: remove extension-based fallback (no longer needed)
- DocumentService: replace leftover ResponseStatusException with DomainException
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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