Define protobuf messages and PluginHooks gRPC service for lifecycle and
system hooks:
- Implemented: returns list of hooks the plugin implements
- OnActivate/OnDeactivate: plugin lifecycle events
- OnConfigurationChange: configuration change notifications
- OnInstall: plugin installation event
- OnSendDailyTelemetry: daily telemetry hook
- RunDataRetention: data retention batch processing
- OnCloudLimitsUpdated: cloud product limit changes
- ConfigurationWillBeSaved: configuration validation/modification
Also adds model types:
- OnInstallEvent: mirrors model.OnInstallEvent
- ProductLimits/FilesLimits/MessagesLimits/TeamsLimits: typed cloud limits
- ConfigJson: JSON blob wrapper for model.Config (too large for typed proto)
Updates Makefile to include new proto file mappings.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
