feat(#29): implement cron job configuration

- Add CronSchedule model to Prisma schema
- Implement CronService with CRUD operations
- Add REST API endpoints for cron management
- Create MoltBot plugin skill definition (SKILL.md)
- TDD: 9 passing tests for CronService

ISSUES/29-cron-config.md

@@ -0,0 +1,54 @@
+# Cron Job Configuration - Issue #29
+
+## Overview
+Implement cron job configuration for Mosaic Stack, likely as a MoltBot plugin for scheduled reminders/commands.
+
+## Requirements (inferred from CLAUDE.md pattern)
+
+### Plugin Structure
+```
+plugins/mosaic-plugin-cron/
+├── SKILL.md          # MoltBot skill definition
+├── src/
+│   └── cron.service.ts
+└── cron.service.test.ts
+```
+
+### Core Features
+1. Create/update/delete cron schedules
+2. Trigger MoltBot commands on schedule
+3. Workspace-scoped (RLS)
+4. PDA-friendly UI
+
+### API Endpoints (inferred)
+- `POST /api/cron` - Create schedule
+- `GET /api/cron` - List schedules
+- `DELETE /api/cron/:id` - Delete schedule
+
+### Database (Prisma)
+```prisma
+model CronSchedule {
+  id          String   @id @default(uuid())
+  workspaceId String
+  expression  String   // cron expression
+  command     String   // MoltBot command to trigger
+  enabled     Boolean  @default(true)
+  createdAt   DateTime @default(now())
+  updatedAt   DateTime @updatedAt
+
+  @@index([workspaceId])
+}
+```
+
+## TDD Approach
+1. **RED** - Write tests for CronService
+2. **GREEN** - Implement minimal service
+3. **REFACTOR** - Add CRUD controller + API endpoints
+
+## Next Steps
+- [ ] Create feature branch: `git checkout -b feature/29-cron-config`
+- [ ] Write failing tests for cron service
+- [ ] Implement service (Green)
+- [ ] Add controller & routes
+- [ ] Add Prisma schema migration
+- [ ] Create MoltBot skill (SKILL.md)