Mitigate security warning from regex with env var (microsoft#283)

### Motivation and Context

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We have to security warning from Code scanning:
https://github.com/microsoft/chat-copilot/security/code-scanning/14
https://github.com/microsoft/chat-copilot/security/code-scanning/15


### Description

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Replace regex with startsWith.


### Contribution Checklist

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [Contribution
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raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Fix Unix deployment of frontend (microsoft#194)

### Motivation and Context
I introduced a bug with
microsoft#165 in the frontend
deployment script

### Description
Use proper Unix commands in the shell script

### Contribution Checklist
- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [Contribution
Guidelines](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Clean deployment scripts usage descriptions (microsoft#181)

### Motivation and Context

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Found copy & paste errors in our deployment scripts usage descriptions.
They don't match the actual options.

### Description
<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->
Clean the usage descriptions for the deployment scripts.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [Contribution
Guidelines](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄