feat(shared,api): add pause + sort_order columns and contracts

Adds server-side pause accounting and activity ordering primitives.
- WorkSession contract gains paused_seconds (number) and paused_at (ISO string | null).
- Activity contract gains sort_order (number); new ReorderActivitiesInput zod.
- work_sessions += paused_seconds (int NOT NULL DEFAULT 0) + paused_at (timestamp_ms nullable).
- activities += sort_order (int NOT NULL DEFAULT 0).
- toWorkSession / toActivity map the new fields; generated migration 0003.

The new fields are additive; existing api/worker/admin tests stay green.

Products affected: SoleLog backend (apps/api), shared contracts (packages/shared)

apps/api/src/lib/work-session.ts

@@ -19,6 +19,8 @@ export function toWorkSession(
     start_time: new Date(row.startTime).toISOString(),
     end_time: row.endTime ? new Date(row.endTime).toISOString() : null,
     duration_seconds: row.durationSeconds ?? null,
+    paused_seconds: row.pausedSeconds ?? 0,
+    paused_at: row.pausedAt ? new Date(row.pausedAt).toISOString() : null,
     status: row.status as WorkSession['status'],
     source: row.source as WorkSession['source'],
     notes: row.notes ?? null,