feat: add nginx-bad-gateway troubleshooting lab

[HimanM]

Description

This PR adds a new troubleshooting lab where users diagnose a 502 Bad Gateway error caused by a port mismatch between Nginx and a Python backend. It also standardizes metadata for several existing labs and fixes a UI race condition in the Stop Lab button.

Type of change

• Bug fix
• New feature
• New Lab

Lab Requirements (If submitting a new lab)

If you are submitting a new BrokenOps lab, please verify:

• The \lab.yaml\ is fully populated.
• The \cloud-init.yaml\ correctly breaks the environment.
• The \�erify.sh\ script correctly asserts if the environment is fixed.
• The \solution.md\ provides the step-by-step solution to fix the environment.
• The \question.md\ provides the question for the lab.
• Follows the LAB_FORMAT.md guidelines.
• MANDATORY: A working \solution.sh\ script is provided to automatically fix the environment. (This is required for our CI verification pipeline).

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas

Closes Issues ?

• closes issue [LAB IDEA] Nginx Bad Gateway #28