fix(frontend): upgrade base image to ubi9 to resolve python vulnerability

[xnaveenx]

Proposed changes

Fixes #5379
Fixes #5314
This PR upgrades the ChaosCenter frontend base image from UBI 8 (ubi-minimal:8.5) to UBI 9 (ubi-minimal:9.7).

Reason for change: The previous UBI 8 base image relied on Python 3.6, which has reached end-of-life and contains known security vulnerabilities. UBI 9 ships with Python 3.9, resolving these issues.

This PR also includes the necessary configuration adjustments (package installation and file permissions) to ensure Nginx runs correctly in the stricter UBI 9 environment.

Types of changes

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• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices applies)

Checklist

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• I have read the CONTRIBUTING doc
• I have signed the commit for DCO to be passed.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

Dependency

• None

Special notes for your reviewer:

Detailed Changes & Rationales:

1. Base Image Upgrade:

   • FROM registry.access.redhat.com/ubi9/ubi-minimal:9.7
   • Why: To move from Python 3.6 to Python 3.9 and fix security vulnerabilities.

2. Package Installation:

   • Added python3-pip to the install command.
   • Why: In UBI 8, pip was bundled with python3. In UBI 9, they are separate packages. Without this, pip3 install pyyaml fails.

3. Permission Fixes (Nginx Crash Resolution):

   • Added touch /run/nginx.pid
   • Added chown/chmod for /var/lib/nginx and /run/nginx.pid
   • Why: UBI 9 has stricter default permissions than UBI 8. The container runs as non-root user 65534. Without explicitly granting ownership of the Nginx temp directories (/var/lib/nginx) and the PID file location, Nginx crashes immediately with "Permission Denied" errors.

Verification Steps Performed:

1. Built the Docker image locally using the new Dockerfile.
2. Deployed the pod in a local Kubernetes cluster.
3. Status Check: Confirmed pod reached Running (1/1) state.
4. Python Check: Executed into the pod and verified python3 --version returns Python 3.9.x.
5. UI Check: Port-forwarded to port 8185 and successfully loaded the Litmus Dashboard, confirming Nginx is serving static assets correctly.