Add manual trigger type and sharing search for automations - #2646

Incremental Code Review Summary

The latest commit correctly addresses all five previously reported issues: non-D1 optimistic concurrency guards are now enforced, resource IDs are carried through automation mutations, sharing state is wired into the editor, and stale event conditions are cleared during trigger transitions. Those stale review threads were resolved before this review.

Two new regressions were found in the follow-up implementation:

• 🔴 HIGH — Specific-user sharing is still summarized as private; opening and saving an already shared automation can reconstruct Personal sharing and revoke all collaborators.
• 🔴 HIGH — The editor always sends condition: null for schedule saves, but the service now rejects any defined condition for non-event triggers, so saving scheduled automations fails.

The manual trigger and stable-ID API changes otherwise follow the intended architecture, with useful coverage around access and transaction behavior.

🧪 Browser testing: Will run after this review (PR touches UI code)