docs: Add redeployment warning

[Shreyas-Microsoft]

Purpose

This pull request updates the deployment documentation to help users avoid common redeployment issues. The main improvement is the addition of a critical warning about the need to create a fresh environment if a .azure folder exists, which helps prevent conflicts and deployment failures during redeployment.

Documentation improvements:

• Added a "Critical: Redeployment Warning" to the "Start Deployment" section, instructing users to create a fresh environment if a .azure folder exists before running azd up.
• Added the same warning to the "Deploy Changes" section to reinforce the need for a fresh environment when redeploying after local modifications.

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

Verify that the following are valid

• ...

Other Information

[github-actions]

🎉 This PR is included in version 1.0.2 🎉

The release is available on GitHub release

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