mrc-6949 Increase API max memory

[EmmaLRussell]

Set java option for max memory to 4GB in the gradle script to allow for pushes of packets with large files.

Also fix an old docker ref for output server in one of the dev scripts/

This has been tested by deploying this branch to https://reside-dev.packit-dev.dide.ic.ac.uk
I was able to push a packet with a file sized >1GB (the file size which Pete has been struggling with) - which had previously failed with the main branch.
The packet in question: https://reside-dev.packit-dev.dide.ic.ac.uk/test-packit-memory/20260622-151516-64ce5178/downloads
Offending file is input file "massive.csv"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.27%. Comparing base (2b61673) to head (6f65e7f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #266   +/-   ##
=======================================
  Coverage   99.27%   99.27%           
=======================================
  Files         205      205           
  Lines        5971     5971           
  Branches     1008     1008           
=======================================
  Hits         5928     5928           
  Misses         42       42           
  Partials        1        1           

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