Auto-reset mappings when address book is changed in profile editor

When editing a profile and switching to a different Starface
address book, the old contact mappings are invalid (different
Starface IDs). Now automatically clears mappings and shows a
notification. Custom address books are already listed as tags.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/StarfaceOutlookSync/UI/ProfileEditorForm.cs

@@ -333,9 +333,23 @@ namespace StarfaceOutlookSync.UI
             };
 
             if (_isNew)
+            {
                 _pm.AddProfile(profile);
+            }
             else
+            {
+                // Wenn Adressbuch gewechselt wurde, Mappings zuruecksetzen
+                if (_existingProfile.StarfaceAddressBook?.TagId != profile.StarfaceAddressBook?.TagId
+                    || _existingProfile.StarfaceAddressBook?.Type != profile.StarfaceAddressBook?.Type)
+                {
+                    _pm.SaveMappings(profile.Id, new List<SyncMapping>());
+                    profile.LastSync = "";
+                    MessageBox.Show(
+                        "Adressbuch wurde geaendert.\nSync-Zuordnungen wurden automatisch zurueckgesetzt.",
+                        "Adressbuch geaendert", MessageBoxButtons.OK, MessageBoxIcon.Information);
+                }
                 _pm.UpdateProfile(profile);
+            }
 
             DialogResult = DialogResult.OK;
             Close();