feat(native-triggers): add summary field to native triggers

[hugocasa]

Summary

• Add optional summary field to native triggers (Nextcloud, Google), matching the pattern already used by schedules and HTTP triggers
• Summary is stored in DB, exposed via API, editable in the trigger editor UI, and round-tripped by the CLI during sync push/pull
• When a summary is set, it is displayed as the trigger label in list views

Test plan

• Create a native trigger via UI, set a summary → verify it persists on reload
• Edit the trigger, change summary → verify it updates
• Check the trigger list view shows the summary as the label
• Export workspace via CLI (wmill sync pull) → confirm the JSON file includes summary
• Edit the summary in the JSON file, push (wmill sync push) → confirm it updates on the server

🤖 Generated with Claude Code

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