Add JMeter stress tests

Add a complete suite of JMeter stress tests including detailed instructions on how to run them. Tests should cover all major functionality of the application and use meaningful, representative load.

This is a substantial amount of work. Please carefully consider scope, complexity, and time commitments before undertaking this work. The ideal person for this work is someone already experienced with Jakarta EE, JMeter, and enterprise stress testing.

Start by reviewing the application's major functionality and the Jakarta EE and JMeter requirements in the issue. Define a representative load plan, build a complete JMeter stress-test suite, and document how to run it. Done means the major functionality is covered, the load is meaningful, and the instructions are complete.

Written by the indexing model from the issue text.