[FEATURE] Add skip-if-missed option for recurring scheduled tasks

When the Claude Desktop app is closed or offline during a scheduled task's cron time, all missed runs fire simultaneously when the app comes back online. This creates "catch-up flooding" where multiple hours' worth of tasks execute at once — producing duplicate or stale results.

For example, three email triage tasks scheduled at 9 AM, 1 PM, and 6 PM all fired at 6:26 AM when the app launched, producing nearly identical briefings.

Request: Add an optional skipIfMissed: true parameter that drops any run whose scheduled time has already passed by more than N minutes (configurable, default perhaps 30). This would prevent catch-up flooding while still allowing brief delays (e.g., app restarting).

Reference: Similar to cron's RANDOM_DELAY and anacron's behavior. GitHub issue #50619 also documents this catch-up flooding behavior.