docs: README.md and docs

docs/usecase-diagram.md

@@ -0,0 +1,53 @@
+# 📊 Heval Light – Use Case Diagram
+
+```mermaid
+%%{init: {'theme': 'neutral'}}%%
+flowchart LR
+    %% Akteure %%
+    user((👤 Benutzer))
+
+    %% Systemcontainer %%
+    subgraph System [Heval Light App]
+        direction TB
+        UC1([Registrieren mit Name, E-Mail, Passwort])
+        UC2([Wohnort automatisch per GPS übernehmen])
+        UC3([Arbeitsort/Schule/Uni eintragen])
+        UC4([Anmelden mit Face ID / Touch ID])
+        UC5([Kalender-Events aus iPhone lesen])
+        UC6([Neue Erinnerung/Termin speichern])
+        UC7([Erinnerung per Sprache hinzufügen])
+        UC8([Push-Notification senden])
+        UC9([Später: KI-Assistent nutzen])
+    end
+
+    %% Externe Systeme %%
+    gps[(📍 GPS / Location API)]
+    sqlite[(🗄 SQLite Datenbank)]
+    iosCal[(📅 iOS Calendar API)]
+    biometrics[(🔐 Face ID / Touch ID)]
+    voiceApi[(🎤 Speech-to-Text API)]
+    pushApi[(🔔 Push Notification Service)]
+    aiApi[(🤖 KI-API OpenAI)]
+
+    %% Beziehungen Benutzer -> Use Cases %%
+    user --> UC1
+    user --> UC2
+    user --> UC3
+    user --> UC4
+    user --> UC5
+    user --> UC6
+    user --> UC7
+    user --> UC8
+    user --> UC9
+
+    %% Beziehungen Use Cases -> Externe Systeme %%
+    UC2 --> gps
+    UC4 --> biometrics
+    UC5 --> iosCal
+    UC6 --> sqlite
+    UC7 --> voiceApi
+    UC8 --> pushApi
+    UC9 --> aiApi
+
+
+```