added docs

docs/frontend-class-diagram.puml

@@ -0,0 +1,86 @@
+@startuml "Frontend Klassendiagramm"
+
+skinparam packageStyle rectangle
+skinparam classAttributeIconSize 0
+skinparam classFontSize 10
+skinparam defaultFontSize 9
+skinparam wrapWidth 100
+skinparam nodesep 30
+skinparam ranksep 30
+
+top to bottom direction
+
+title Frontend (Expo React Native)
+
+' ===== SCREENS =====
+package "Screens" #87CEEB {
+    class LoginScreen
+    class RegisterScreen
+    class CalendarScreen
+    class ChatScreen
+    class EventDetailScreen
+    class NoteScreen
+}
+
+' ===== COMPONENTS =====
+package "Components" #FFA07A  {
+    class EventCard
+    class ChatBubble
+    class EventConfirmDialog
+    class MonthSelector
+}
+
+' ===== SERVICES =====
+package "Services" #90EE90 {
+    class ApiClient {
+        +get()
+        +post()
+        +put()
+        +delete()
+    }
+    class AuthService
+    class EventService
+    class ChatService
+}
+
+' ===== STORES =====
+package "Stores" #FFD700 {
+    class AuthStore {
+        ' +user
+        ' +token
+    }
+    class EventsStore {
+        ' +events
+    }
+}
+
+' ===== MODELS =====
+package "Models (shared)" #D3D3D3 {
+    class User
+    class CalendarEvent
+    class ChatMessage
+}
+
+' ===== RELATIONSHIPS =====
+
+' Screens -> Services
+LoginScreen --> AuthService
+CalendarScreen --> EventService
+ChatScreen --> ChatService
+NoteScreen --> EventService
+
+' Screens -> Components
+CalendarScreen --> EventCard
+ChatScreen --> ChatBubble
+ChatScreen --> EventConfirmDialog
+
+' Services -> ApiClient
+AuthService --> ApiClient
+EventService --> ApiClient
+ChatService --> ApiClient
+
+' Services -> Stores
+AuthService --> AuthStore
+EventService --> EventsStore
+
+@enduml