Add support for creating stateless backends

[StpMax]

This PR adds the ability to generate and run stateless backend applications.
This is the simplest possible solution with minimal additions to the system prompt. However, it works quite stably for small tasks. The solution will be improved in the future.

Here's how it works:

• Artifacts should be generated in a separate folder, so the server .py file and frontend HTML will be located in the same directory.
• The agent should create a specification for the frontend/backend/API (note: without instructions on how to create the specification, the agent usually makes it very brief)
• The agent implements the artifacts and runs the backend in the scratchpad with action='serve', which immediately returns control to the main loop.

[entelligence-ai-pr-reviews]

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Confidence Score: 5/5 - Safe to Merge

Safe to merge — this PR adds support for creating stateless backends and has passed automated review with no issues identified across logic, correctness, security, or performance dimensions. The implementation appears clean with no unresolved comments from prior reviews and no new concerns raised during analysis. The feature addition is self-contained and does not introduce regressions or problematic patterns.

Key Findings:

• No logic, correctness, security, or performance issues were identified by the automated review pipeline across all changed files.
• No pre-existing unresolved review comments were carried into this PR, indicating a clean review history.
• The PR is narrowly scoped to adding stateless backend creation support, reducing blast radius and integration risk.
• Heuristic analysis returned zero critical, significant, or medium-severity findings, supporting a confident merge recommendation.

[torrmal]

this is good, we need to make sure tihs work all the way to this repo https://github.com/mindsdb/cowork
as that one assumes the artifacts hav e aspecific location, etc.
in that cowork repo, it would be amazing if there was a proxy endpoint for scratchpad:server endpoints, so all requests from the artifact are going thorugh an endpoint that later we can secure with some sort of authentication for sharing,
@StpMax