fix(server): ensure server exists before deletion

[DuarteMartinho]

Issue: #1572

🐞 Bug Summary

When attempting to delete a virtual server that is not found - it returns a status code 400 with the message not found

🧩 Affected Component

Select the area of the project impacted:

• mcpgateway - API
• mcpgateway - UI (admin panel)
• mcpgateway.wrapper - stdio wrapper
• Federation or Transports
• CLI, Makefiles, or shell scripts
• Container setup (Docker/Podman/Compose)
• Other (explain below)

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🔁 Steps to Reproduce

1. Go to /docs
2. Go to DELETE /servers/{server_id}
3. Enter your bearer token
4. Enter a random string of an id that does not exist for example vs-server-id-not-found

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🤔 Expected Behavior

What should have happened instead?
The behaviour should return status 404

📓 Logs / Error Output

Paste any relevant stack traces or logs here.
⚠️ Do not paste secrets, credentials, or tokens.

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🧠 Environment Info

You can retrieve most of this from the /version endpoint.

Key	Value
Version or commit	0.9.0
Runtime	Python 3.12.10
Platform / OS	macOS
Container	none

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🧩 Additional Context (optional)

Looking at DELETE /gateways/{gateway_id} there is a get_gateway so I just added the same to delete_server See here

[DuarteMartinho]

Fixed:

[crivetimihai]

Closed #1572

[crivetimihai]

I don't have access to rebase and push to this branch, so I created #1592 instead. Thank you!