feat(cron): support configurable run timeouts

[caiopizzol]

Cron jobs need an explicit runtime budget because long data refreshes can legitimately exceed Moor’s existing ten-minute exec limit. This keeps the current default while allowing operators to raise it per cron.

• Preserves the ten-minute default for existing jobs
• Validates and exposes the timeout consistently across API, UI, contract, and MCP
• Adds migration coverage and end-to-end scheduler tests

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Summary by cubic

Adds configurable per-cron run timeouts with a 10-minute default, so long-running jobs can exceed the previous limit. The timeout is validated, stored, and used during cron execution.

• New Features

  • Database: added crons.timeout_ms (default 600,000 ms); migration v20.
  • API: create/update accept timeout_ms; strict validation (1 minute to 7 days); default applied if unset; scheduler passes timeout to container exec.
  • Web UI: cron editor adds a timeout (minutes) with inline validation; list shows a formatted timeout.
  • Contract (@moor-sh/contract): types include timeout_ms; exported CRON_TIMEOUT_* constants and validateCronTimeoutMs.
  • MCP tools: moor_cron_create/moor_cron_update accept and forward timeout_ms; tool descriptions and README document the default and 7-day max.
  • Tests: added migration, API route, validator, MCP tool, and execution coverage.

• Migration

  • No action required; existing crons default to 10 minutes automatically.

^{Written for commit 7f61bfe. Summary will update on new commits.}