Remove agent script execution feature

[mrostan]

What's new?

Removes the /api/v1/agent/execute_script endpoint and its RestrictedPython
executor, which allowed callers to send Python scripts to be run on the agent.
The feature is unused and is flagged by customer security reviews.

• Delete apollo/agent/scripts.py (the RestrictedPython executor)
• Remove Agent.execute_script / Agent._execute_script and AgentEvaluationUtils.execute_script
• Remove the /api/v1/agent/execute_script Flask route
• Drop the RestrictedPython dependency (requirements.in / requirements.txt)
• Remove the script tests and sample-script fixtures

Related PRs

• agent-base — removes the now-unused AgentScript model + constants
• data-collector — removes the subsystem that called this endpoint

Testing

• Unit tests pass locally (1122 passed)
• Integration tested on dev

Merge ordering

Part of a 3-repo change. apollo-agent no longer imports anything from the
removed agent-base symbols, so CI passes against the currently-pinned
agent-base. Coordinated dev rollout: agent-base + apollo-agent first, then
bump data-collector's mcd-agent pin (which drops restrictedpython from its
lockfile).

🤖 Generated with Claude Code

[mrostan]

⚠️ Do not merge to main as-is. This branch temporarily pins agent-base @ ...@dev (commit 21c9b6c) for dev integration testing against the agent-base change (monte-carlo-data/agent-base#7, already on agent-base dev). Before merging to main, swap the pin back to a proper agent-base release tag (cut a new agent-base release after #7 merges to main, then bump requirements.in/requirements.txt here).