Add dockerfile for local rootless build

[karensantana]

Proposed changes

This PR adds a new Dockerfile for building and running the local Agent environment with a rootless NGINX setup.
The goal is to simplify local development and testing workflows while aligning the container runtime configuration more closely with modern container security best practices. Running NGINX without root privileges reduces the need for elevated permissions inside the container and better reflects production environments that enforce non-root execution policies.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[github-actions]

✅ All required contributors have signed the F5 CLA for this PR. Thank you!
_{Posted by the CLA Assistant Lite bot.}

[karensantana]

🎉 Thank you for your contribution! It appears you have not yet signed the F5 Contributor License Agreement (CLA), which is required for your changes to be incorporated into an F5 Open Source Software (OSS) project. Please kindly read the F5 CLA and reply on a new comment with the following text to agree:

I have hereby read the F5 CLA and agree to its terms

You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.

I have hereby read the F5 CLA and agree to its terms

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.00%. Comparing base (0938f7c) to head (0e46238).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1691      +/-   ##
==========================================
+ Coverage   84.86%   85.00%   +0.13%     
==========================================
  Files         104      104              
  Lines       13579    13579              
==========================================
+ Hits        11524    11543      +19     
+ Misses       1542     1522      -20     
- Partials      513      514       +1     

see 6 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0938f7c...0e46238. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[karensantana]

🎉 Thank you for your contribution! It appears you have not yet signed the F5 Contributor License Agreement (CLA), which is required for your changes to be incorporated into an F5 Open Source Software (OSS) project. Please kindly read the F5 CLA and reply on a new comment with the following text to agree:
I have hereby read the F5 CLA and agree to its terms
You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.

I have hereby read the F5 CLA and agree to its terms

recheck

[karensantana]

🎉 Thank you for your contribution! It appears you have not yet signed the F5 Contributor License Agreement (CLA), which is required for your changes to be incorporated into an F5 Open Source Software (OSS) project. Please kindly read the F5 CLA and reply on a new comment with the following text to agree:

I have hereby read the F5 CLA and agree to its terms

You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.

recheck

[karensantana]

I have hereby read the F5 CLA and agree to its terms

[karensantana]

recheck