Feature/add task report

[JheisonMB]

• Add RunStatus enum (pending, in_progress, success, error, timeout, missed)
• Extend RunLog with UUID id, status, summary, and timeout_at
• Add timeout_minutes to Task and Watcher (default: 15)
• Migrate runs table from INTEGER to TEXT PRIMARY KEY with new columns
• Implement task locking: executor checks for active runs before launching
• Record missed runs when a trigger arrives while task is locked
• Add task_report MCP tool for agents to report execution status
• Wrap user prompts with structured task_report instructions
• Lazy timeout resolution (no background polling)
• Add uuid crate dependency
• Update README with badges, execution runs docs, and tool count