* fix(backend): validate business-profile logo uploads by content, not filename
The upload route skipped the shared validateFileType() helper every
sibling upload route uses, and derived the stored extension from the
client-supplied filename. A file could declare an image MIME type
while carrying an executable/HTML extension and arbitrary content,
then be served same-origin via the mass-assignable logoPath field.
* fix(backend): content-sniff business-profile logo uploads too
fileFilter paired the claimed MIME type against the extension but
never verified the actual bytes matched, unlike other upload routes
that already call validateFileContent(). Defense-in-depth: the
extension-confusion XSS itself was already closed (stored extension
is derived from the validated MIME, not client input), this closes
the remaining gap where declared-vs-actual content can still diverge.
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Co-authored-by: Paul Nothaft <paul@MacStudio-von-Paul.local>
Paul Nothaft
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