Enforce primitive size limits (DoS prevention)

[las7]

Problem

Unbounded ints, strings, and collections enable memory exhaustion attacks.

Proposed change

Enforce limits on:

• max string length
• max list/dict/set size
• max integer bit length
• max recursion depth

Acceptance criteria

• Violations terminate execution with clear error.
• Limits configurable per job type.

[las7]

Reviewed. Still valid for restricted/LLM execution. Existing container memory, output, artifact, input, pids, and file-size limits reduce blast radius, but they do not enforce primitive-level limits inside Python. Proposed plan: add restricted_python configurable limits for literal string/bytes sizes, collection literal sizes, int bit length, recursion depth, and safe range bounds; combine with runtime operation budgets from #13. Leaving open.