Environment variables in `404.html` page aren't getting replaced with
their values. This PR fixes that.
## Automation
/test sanity
### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results -->
> [!WARNING]
> Workflow run:
<https://github.com/appsmithorg/appsmith/actions/runs/12005727044>
> Commit: 56b10fddf2ee7ed180ed59845b6f0223cd26b06a
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=12005727044&attempt=1"
target="_blank">Cypress dashboard</a>.
> Tags: @tag.Sanity
> Spec:
> It seems like **no tests ran** 😔. We are not able to recognize it,
please check <a
href="https://github.com/appsmithorg/appsmith/actions/runs/12005727044"
target="_blank">workflow here</a>.
> <hr>Mon, 25 Nov 2024 08:48:10 UTC
<!-- end of auto-generated comment: Cypress test results -->
## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [x] No
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **New Features**
- Improved dynamic retrieval of environment variables for better
integration with environment-specific settings in the 404 error page.
- Enhanced handling of HTML files, including the 404 page, during the
configuration process.
- **Bug Fixes**
- Improved error handling for missing SSL certificates and custom
domains.
- **Documentation**
- Updated logic for processing HTML files to ensure correct paths and
configurations are applied.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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