New model types: TaskStatus, TaskSummary, LabelInfo, ItemSummary.
GRDB records: TaskRecord, LabelRecord, ItemLabelRecord, DeferralRecord.
Database migrations v3_task, v3_label, v3_deferral with indexes.
MailStore query extensions for labels, item-labels, deferrals, task cache.
TaskStore module wrapping MailStore. Tests for all v3 tables and records.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
