[BUG] Actual uploaded file size is not validated before ingestion

[Yehor-Makarenko]

[BUG] Actual uploaded file size is not validated before ingestion
Summary
The 500 MiB file-size limit can be bypassed by sending an incorrect fileBytes value when creating a document. After uploading a file whose actual size exceeds the limit, the ingestion endpoint accepts it with 200 OK.
The backend appears to trust client-provided metadata without verifying the actual S3 object size.
Test data used: https://drive.google.com/file/d/1-6D_yIDToffrz07RUpEkEwISAuJ0Aq-4/view?usp=drive_link

Steps to reproduce

Sign in with a valid user account.
Prepare a valid PDF with an actual size of 524,298,486 bytes (500.01 MiB).
Send POST /api/v1/documents but specify a smaller fileBytes value:
{
"title": "pdf over 500 mb",
"presetId": 1,
"fileName": "invalid-pdf-500.01-MiB.pdf",
"fileBytes": 52429848
}
Note the created document ID and presigned upload URL.
Upload the actual 524,298,486-byte PDF through the presigned URL.
Wait until the S3 PUT request completes successfully.
Send:
POST http://98.90.162.1/api/v1/documents/139/ingest
Content-Type: application/json
{file}
Observe the response.
Expected result
The system verifies the actual uploaded object size instead of relying only on the client-provided fileBytes.
A file larger than 524,288,000 bytes (500 MiB) is rejected either during upload or before ingestion. The ingestion endpoint returns a controlled 4xx response, preferably 413 Content Too Large, and no pages are created.

Actual result
The ingestion endpoint accepts the oversized PDF:
Status: 200 OK
Response: null
The actual file is 524,298,486 bytes, even though the document creation request declared only 52,429,848 bytes.

Environment
Application: http://98.90.162.1/
API: http://98.90.162.1/api/v1
Document ID: 139
Declared size: 52,429,848 bytes
Actual size: 524,298,486 bytes (500.01 MiB)
OS: macOS 26.5.1 (25F80)

Severity / priority
High / High

Screenshots or logs
POST /api/v1/documents
{
"title": "pdf over 500 mb",
"presetId": 1,
"fileName": "invalid-pdf-500.01-MiB.pdf",
"fileBytes": 52429848
}

PUT
Uploaded file size: 524,298,486 bytes
Status: Successful

POST /api/v1/documents/139/ingest
Payload: {}
Status: 200 OK
Response: null