I’m ready to commission a complete, production-grade time-tracking solution, starting with a robust web app that delivers three must-have capabilities on day one: a true one-click timer, reliable manual time entry, and intuitive project / task management. Data must save locally when offline and auto-sync as soon as a connection returns, so users can stay productive anywhere. From the same interface, I need users to generate polished reports in PDF, CSV, and XLS formats as well as see at-a-glance profitability dashboards that pull in real-time billable vs. cost data. A privacy-minded activity tracker should optionally log app and website usage, and I’d like calendar integration so meetings appear alongside tracked work. All data—time logs, projects, tasks, usage events—has to flow through a clean JSON REST API, making hooks for Slack slash-commands or pushes into Asana / Jira straightforward. Cross-platform reach is non-negotiable, yet the first milestone focuses on the web. Once the web app is stable, I aim to reuse the same API and business logic for native iOS / Android apps and lightweight Windows / Mac clients. If forking a mature open-source base such as Kimai or SolidTime lets us move faster while still meeting these requirements, propose it; otherwise outline your preferred stack. Deliverables I will use for acceptance: • Web app implementing one-click timer, manual entry, and project / task CRUD with offline sync. • Export engine producing PDF, CSV, and XLS on demand. • Dashboard surfaces showing margin and utilization metrics. • Opt-in activity tracker with privacy settings. • Calendar connector (Google / Outlook) surfacing events. • Fully documented JSON REST API, including sample calls for Slack, Asana, and Jira. • Source code, tests, and deployment scripts. Show me relevant experience building SaaS-style apps, handling offline sync, or extending time-tracking tools, and outline an estimated timeline for each deliverable.