vector: bound request buffering before authentication and document installation (#12537)

* s3vectors: bound body buffering before authentication

* docs: include vector engine installation and source builds

* s3vectors: prevent MIME sniffing of JSON error responses

* docs: load vector Cargo configuration when building from source

* docs: note the native protoc requirement for Windows vector builds

* docs: make vector source checkout and working directory explicit

* ci: handle deb822 sources during Ubuntu mirror failover

* ci: bound Ubuntu mirror attempts and reject partial index updates

weed/command/s3.go

@@ -760,6 +760,7 @@ func (s3opt *S3Options) vectorsRouter(s3ApiServer *s3api.S3ApiServer, grpcDialOp
 	vectorsServer.SetEncryptionChecker(s3api.GetSSES3KeyManager().IsConfigured)
 	vectorsServer.SetDescribe(describe)
 	vectorsServer.SetLimiter(s3ApiServer.Limit)
+	vectorsServer.SetRequestLimits(int64(*s3opt.concurrentFileUploadLimit), int64(*s3opt.concurrentUploadLimitMB)*1024*1024)
 	vectorsServer.RegisterRoutes(vectorsRouter)
 	return vectorsRouter
 }