fix: Add chat widget guide and improve URL validation and hooks

[Harsh-Microsoft]

Purpose

This pull request introduces several improvements focused on security, documentation, and deployment configuration. The most significant changes include enhancing endpoint validation logic to prevent security issues, adding comprehensive documentation for the embeddable chat widget, and updating deployment hooks for interactive execution.

Security improvements:

• Refactored endpoint validation in chat-app/backend/app/utils/voice_utils.py to use a robust _hostname_matches helper, ensuring hostnames match exactly or as subdomains, and replacing insecure substring checks in both resolve_endpoint and is_valid_realtime_endpoint. This guards against incomplete URL sanitization and related security risks.

Documentation updates:

• Added a new guide, documents/EmbeddableWidgetGuide.md, detailing the architecture, build, embedding process, and validation steps for the chat widget, including local development and cross-origin considerations.
• Removed the outdated documents/customer-chatbot-product-roadmap.md, which previously described the product roadmap and implementation sequence for the embeddable widget and related accelerator components.

Deployment configuration:

• Changed the interactive flag from false to true in both the Windows and POSIX hooks sections of azure.yaml, enabling interactive execution for deployment hooks. [1] [2]

Does this introduce a breaking change?

• Yes
• No

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information