fix: Deploy-FinOpsHub fails in Cloud Shell/Linux (#665)

[RolandKrummenacher]

🛠️ Description

Initialize $toolkitPath before the try block to ensure cleanup works even if an early failure occurs. The $toolkitPath variable was being set inside the try block, but the finally block attempted to use it for cleanup. If an error occurred before $toolkitPath was set (e.g., when $env:temp is not defined on Linux/Cloud Shell), the cleanup failed with "Cannot bind argument to parameter 'Path' because it is null", masking the real error.

Fixes #665

📷 Screenshots

N/A - Code fix only

📋 Checklist

🔬 How did you test this change?

• 🤏 Lint tests
• 🤞 PS -WhatIf / az validate
• 👍 Manually deployed + verified
• 💪 Unit tests
• 🙌 Integration tests

🙋‍♀️ Do any of the following that apply?

• 🚨 This is a breaking change.
• 🤏 The change is less than 20 lines of code.

📑 Did you update docs/changelog.md?

• ✅ Updated changelog (required for dev PRs)
• ➡️ Will add log in a future PR (feature branch PRs only)
• ❎ Log not needed (small/internal change)

📖 Did you update documentation?

• ✅ Public docs in docs (required for dev)
• ✅ Public docs in docs-mslearn (required for dev)
• ✅ Internal dev docs in docs-wiki (required for dev)
• ✅ Internal dev docs in src (required for dev)
• ➡️ Will add docs in a future PR (feature branch PRs only)
• ❎ Docs not needed (small/internal change)