docs: add sidebar navigation with grouped sections

_Sidebar.md

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+### 🌿 [CannaManage](Home)
+
+---
+
+**📋 Planning**
+- [Project Charter](CannaManage-01-Charter)
+- [User Stories](CannaManage-02-UserStories)
+- [Retrospective](CannaManage-10-Retrospective)
+
+**🏗️ Architecture**
+- [System Design](CannaManage-03-Architecture)
+- [Flow Charts](CannaManage-04-Flowcharts)
+- [API Reference](CannaManage-05-API)
+
+**🎨 Design**
+- [Wireframes & Mockups](CannaManage-06-Wireframes)
+
+**💻 Development**
+- [Coding Standards](CannaManage-07-CodingStandards)
+- [Test Plan](CannaManage-08-TestPlan)
+- [Deployment Guide](CannaManage-09-Deployment)
+
+---
+
+**📊 Sprint Status**
+
+| Sprint | Status |
+|--------|--------|
+| 1 — Domain | ✅ |
+| 2 — API | ✅ |
+| 3 — Portal | 📋 |