Mute poll failure alerts

[dantheuber]

Summary

Adds the ability to mute poll failure alerts for specific services. Previously, mutes only targeted individual dependency instances (dependency_id) or all instances of a dependency type (canonical_name). Poll failure events (poll_error) are service-level and don't carry a dependencyId, so they bypassed the existing mute system entirely. This adds service_id as a third mutually-exclusive mute scope — service mutes only suppress poll_error alerts and do not affect status_change alerts for dependencies within that service.

Changes

Database

• New migration 032_add_service_mutes — recreates alert_mutes with service_id TEXT column (FK → services), updated CHECK constraint enforcing exactly one of three targets, and unique index on (team_id, service_id)
• Registered migration in migrate.ts

Server

• AlertMute / CreateAlertMuteInput types updated with service_id field
• IAlertMuteStore + AlertMuteStore: new isServiceMuted() method, create() now includes service_id
• AlertService.processEvent(): service mute check added before dependency mute check for poll_error events — records history as muted and returns early
• validateMuteCreate(): accepts service_id as third scope, validates exactly one target provided
• Mute routes updated: create verifies service ownership, list/admin enrich service_name, delete includes service_id in audit log

Client

• AlertMute / CreateAlertMuteInput types updated
• AlertMutes.tsx: new "Service (poll failures)" scope option, service ID input field, table shows "Service" type and service name for service mutes

Docs

• 02-data-model.md: updated schema, indexes, and migration history
• 04-api-reference.md: added alert mute endpoint documentation

Testing

• New/updated tests included
• All tests pass (npm test)
• Linting passes (npm run lint)

New server tests:

• Service mute CRUD via API (create, reject bad ownership, reject nonexistent service, reject multi-target, list enrichment)
• AlertService: poll_error suppressed when service muted, poll_error dispatched when not muted, status_change not suppressed by service mute
• Validation: updated expectations for three-target error message

New client tests:

• Service mute renders correctly in table (type + name)
• Service scope form shows Service ID input

Results: 2987 server tests passed, 1442 client tests passed

Checklist

• I have read the Contributing Guidelines
• I agree to the Contributor License Agreement
• My changes do not introduce security vulnerabilities
• Documentation updated (if applicable)