feat: Add Milestone 3 documentation including feature testing plan, demo notes, and demo flow details

- Introduced comprehensive testing plan for Milestone 3 in m3-client-note.md
- Documented feedback and suggestions from demo sessions in m3-notes.md
- Created detailed demo flow for Milestone 3 in m3.md, outlining user interactions and expected outcomes
- Added planning tasks for Milestone 4 in m4-planning.md, covering backend and frontend development tasks, research, and business tasks

docs/DATACONNECT_GUIDES/DIAGRAMS/uml/user_uml_diagram.mmd

@@ -0,0 +1,71 @@
+
+classDiagram
+direction TB
+    class User {
+      id: String
+      email: String
+      fullName: String
+      role: UserBaseRole
+    }
+
+    class Staff {
+      id: UUID
+      userId: String
+      fullName: String
+      ownerId: UUID
+      hubId: UUID
+      rollId: UUID
+      status: BackgroundCheckStatus
+    }
+
+    class Vendor {
+      id: UUID
+      userId: String
+      companyName: String
+    }
+
+    class Business {
+      id: UUID
+      userId: String
+      businessName: String
+    }
+
+    class TeamMember {
+	    id: UUID
+	    teamId: UUID
+	    userId: String
+	    role: TeamMemberRole
+    }
+
+    class ActivityLog {
+      id: UUID
+      userId: String
+      activityType: ActivityType
+    }
+
+    class UserConversation {
+      conversationId: UUID
+      userId: String
+    }
+
+    class Conversation {
+      id: UUID
+      conversationType: ConversationType
+    }
+    
+    class Message{
+      id: UUID
+      conversationId: UUID
+      content: String
+    }
+
+    User <|-- Staff 
+    User <|-- Business 
+    User <|-- Vendor 
+    User <|-- TeamMember 
+
+
+    User "1" -- "*" ActivityLog : logs
+    User "1" -- "*" UserConversation : participates in
+    UserConversation "*" -- "1" Conversation : is part of
+    Conversation "1" -- "*" Message : has