fix(media): infer generic upload types safely

[aiirvizionz]

Summary

• avoids defaulting empty media upload MIME types to video/mp4
• accepts explicit allowed video MIME types, or infers from .mp4, .webm, and .mov filenames when the client sends an empty/generic type
• rejects generic uploads like payload.txt instead of storing them as videos

Tests

• node --test tests\media-upload-type.test.mjs
• node --test tests\http-range.test.mjs
• node_modules\.bin\tsc.CMD -p tsconfig.json --noEmit
• git diff --check