fix: Update model references from GPT-4o to GPT-5.1 across documentation and scripts

[vishalsvs7]

Purpose

Update model references from GPT-4o to GPT-5.1 across documentation and scripts

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.

[Copilot]

Pull request overview

Updates the accelerator’s documented and scripted default GPT model from gpt-4o to gpt-5.1, aligning quota-check tooling and sample configuration with the model referenced by the infrastructure defaults.

Changes:

• Update backend .env.sample agent model deployment defaults to gpt-5.1.
• Update quota-check scripts’ default model identifiers/capacities to gpt-5.1.
• Update documentation examples and quota guidance from GPT-4o to GPT-5.1.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/backend/.env.sample	Updates sample agent model deployment env vars to gpt-5.1.
scripts/quota_check_params.sh	Updates default model:capacity pair to gpt-5.1:150.
scripts/checkquota.sh	Updates the quota model key to OpenAI.GlobalStandard.gpt-5.1.
docs/quota_check.md	Updates quota guidance and example invocations to gpt-5.1.
docs/EXAMPLE-CustomizingAzdParameters.md	Updates model name example to gpt-5.1 (but needs a parameter name fix).
docs/AzureGPTQuotaSettings.md	Updates portal guidance to reference GPT-5.1.

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