[Feature] partial hashing for faster and less problematic uploads of large files

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature Somewhat inspired by #18991 and my attempt to upload a 35 GiB video from Safari. Currently, Immich performs a full hash on the client and another on the server to guarantee that no duplicate files are present. Client-provided hashes are not trusted, which is a good choice, but this may cause performance issues or even make uploads impossible on some clients and browsers. What I believe would be an improvement is the client-side duplicate check: Checking file size is faster than computing a hash. A partial hash is usually fine for a high-entropy file such as a video. For this reason, I believe a cut-off size should be decided and, only for files above it, the duplicate checker should base itself on the file size plus the hash of the first N MB of the file. If the file is "the same at the start" because it is a different va…