refactor: Improve about dialog with better layout and clickable repository link

- Convert about dialog from messagebox to custom Toplevel window
- Improve text formatting and readability with proper spacing
- Make Git repository link clickable (opens in browser with webbrowser module)
- Better layout with aligned labels and structured information display
- Add close button for better user experience

gui.py

@@ -10,6 +10,7 @@ from pathlib import Path
 import threading
 import re
 import json
+import webbrowser
 from pdf_to_ics import extract_dienstplan_data, create_ics_from_dienstplan
 from update_checker import check_for_updates, get_current_version
 
@@ -263,22 +264,125 @@ class PDFtoICSGUI:
     
     def show_about_dialog(self):
         """Zeige About-Dialog mit Programminformationen"""
+        about_window = tk.Toplevel(self.root)
+        about_window.title("Über dieses Programm")
+        about_window.geometry("500x350")
+        about_window.resizable(False, False)
+        
+        # Zentriere das Fenster
+        about_window.transient(self.root)
+        about_window.grab_set()
+        
+        # Header
+        header = tk.Label(
+            about_window,
+            text="PDF zu ICS Konverter",
+            font=("Arial", 16, "bold"),
+            bg="#2c3e50",
+            fg="white",
+            pady=15
+        )
+        header.pack(fill=tk.X)
+        
+        # Content Frame
+        content = tk.Frame(about_window, padx=20, pady=20)
+        content.pack(fill=tk.BOTH, expand=True)
+        
+        # Version
         version = get_current_version()
-        about_text = f"""PDF zu ICS Konverter - Dienstplan Importer
-Version {version}
+        version_label = tk.Label(
+            content,
+            text=f"Version {version}",
+            font=("Arial", 11, "bold"),
+            fg="#2c3e50"
+        )
+        version_label.pack(anchor=tk.W, pady=(0, 15))
         
-Entwickler: Sebastian Köhler
-Firma: Webfarben
-Kontakt: kontakt@webfarben.de
+        # Info-Texte
+        info_texts = [
+            ("Firma:", "Webfarben"),
+            ("Programmierer:", "Sebastian Köhler"),
+            ("Kontakt:", "kontakt@webfarben.de"),
+        ]
         
-Git Repository:
-https://git.file-archive.de/webfarben/pdf_to_ics.git
+        for label, value in info_texts:
+            frame = tk.Frame(content)
+            frame.pack(anchor=tk.W, pady=3, fill=tk.X)
             
-Ein Programm zur Konvertierung von Dienstplan-PDFs
-zu ICS-Kalenderdateien für einfaches Importieren
-in Kalenderprogramme."""
+            label_widget = tk.Label(
+                frame,
+                text=label,
+                font=("Arial", 10, "bold"),
+                width=15,
+                anchor=tk.W
+            )
+            label_widget.pack(side=tk.LEFT)
             
-        messagebox.showinfo("Über dieses Programm", about_text)
+            value_widget = tk.Label(
+                frame,
+                text=value,
+                font=("Arial", 10),
+                fg="#34495e"
+            )
+            value_widget.pack(side=tk.LEFT, padx=(5, 0))
+        
+        # Git Repository mit Link
+        repo_frame = tk.Frame(content)
+        repo_frame.pack(anchor=tk.W, pady=(15, 0), fill=tk.X)
+        
+        repo_label = tk.Label(
+            repo_frame,
+            text="Repository:",
+            font=("Arial", 10, "bold"),
+            width=15,
+            anchor=tk.W
+        )
+        repo_label.pack(side=tk.LEFT)
+        
+        repo_url = "https://git.file-archive.de/webfarben/pdf_to_ics.git"
+        repo_link = tk.Label(
+            repo_frame,
+            text=repo_url,
+            font=("Arial", 10, "underline"),
+            fg="#3498db",
+            cursor="hand2"
+        )
+        repo_link.pack(side=tk.LEFT, padx=(5, 0))
+        repo_link.bind("<Button-1>", lambda e: webbrowser.open(repo_url))
+        
+        # Beschreibung
+        desc_frame = tk.Frame(content)
+        desc_frame.pack(anchor=tk.W, pady=(20, 0), fill=tk.BOTH, expand=True)
+        
+        desc_text = tk.Text(
+            desc_frame,
+            height=4,
+            font=("Arial", 9),
+            fg="#34495e",
+            wrap=tk.WORD,
+            relief=tk.FLAT,
+            bg=about_window.cget("bg")
+        )
+        desc_text.insert(tk.END, 
+                        "Ein Programm zur Konvertierung von Dienstplan-PDFs "
+                        "zu ICS-Kalenderdateien für einfaches Importieren "
+                        "in Kalenderprogramme.")
+        desc_text.config(state=tk.DISABLED)
+        desc_text.pack(fill=tk.BOTH, expand=True)
+        
+        # Close Button
+        close_btn = tk.Button(
+            about_window,
+            text="Schließen",
+            command=about_window.destroy,
+            bg="#3498db",
+            fg="white",
+            font=("Arial", 10, "bold"),
+            padx=30,
+            pady=8,
+            cursor="hand2"
+        )
+        close_btn.pack(pady=(0, 15))
         
         
     def save_config(self):