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/db/schema.ts

@@ -124,6 +124,7 @@ export const activities = sqliteTable('activities', {
     .$type<string[]>()
     .notNull()
     .default(['Kurk', 'Berk', '3D']),
+  sortOrder: integer('sort_order').notNull().default(0),
   createdAt: integer('created_at', { mode: 'timestamp_ms' })
     .default(sql`(cast(unixepoch('subsecond') * 1000 as integer))`)
     .notNull(),
@@ -144,6 +145,8 @@ export const workSessions = sqliteTable(
     startTime: integer('start_time', { mode: 'timestamp_ms' }).notNull(),
     endTime: integer('end_time', { mode: 'timestamp_ms' }), // null = active
     durationSeconds: integer('duration_seconds'),
+    pausedSeconds: integer('paused_seconds').notNull().default(0),
+    pausedAt: integer('paused_at', { mode: 'timestamp_ms' }), // null = running
     status: text('status').notNull().default('active'), // 'active' | 'completed' | 'discarded'
     source: text('source').notNull().default('app'), // 'app' | 'manual'
     notes: text('notes'),