chore(templates): modernize GitHub issue templates from legacy .md to .yml format

[katriendg]

Problem

The existing issue templates use the legacy .md format which lacks structured form inputs.

Current State

File	Format	Issue
bug_report.md	Legacy .md	No structured form inputs; relies on contributors following comment blocks
feature_request.md	Legacy .md	No structured form inputs
documentation_request.md	Legacy .md	No structured form inputs
blueprint_request.md	Legacy .md	No structured form inputs

Required Changes

1. Convert Templates to .yml Format

Convert each legacy template to GitHub's form-based .yml format with structured inputs:

bug_report.md → bug-report.yml

• Component dropdown (Terraform, Bicep, Blueprints, GitHub Actions, Documentation)
• Environment fields as structured inputs (OS, CLI versions, Terraform/Bicep/K8s versions)
• Required reproduction steps textarea
• Sensitive data warning as markdown preamble

feature_request.md → feature-request.yml

• Component checkboxes
• Problem statement textarea (required)
• Proposed solution textarea (required)
• Benefits textarea

documentation_request.md → documentation-request.yml

• Documentation area dropdown
• Current issue textarea (required)
• Suggested improvement textarea (required)
• Willingness to contribute checkbox

blueprint_request.md → blueprint-request.yml

• Implementation type dropdown (Terraform, Bicep, Both)
• Target architecture textarea (required)
• Components needed textarea
• Azure services textarea

2. Verify/Create Labels

Ensure these labels exist on the repository (referenced in CONTRIBUTING.md):

• bug
• enhancement
• documentation
• blueprint
• needs-repro
• needs-fix
• critical

Acceptance Criteria

• bug_report.md converted to bug-report.yml with form-based inputs
• feature_request.md converted to feature-request.yml with form-based inputs
• documentation_request.md converted to documentation-request.yml with form-based inputs
• blueprint_request.md converted to blueprint-request.yml with form-based inputs
• All referenced labels verified to exist on the repository
• Sensitive data warning preserved in all new templates as markdown preamble