fix: address PR #574 review comments

Restore contact email/birthday/nickname data and per-event calendar
source that were silently dropped during response model wrapping.
Remove dead elif branches in OAuth deck tests, add regression tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextcloud_mcp_server/server/contacts.py

@@ -8,6 +8,7 @@ from nextcloud_mcp_server.context import get_client
 from nextcloud_mcp_server.models.contacts import (
     AddressBook,
     Contact,
+    ContactField,
     ListAddressBooksResponse,
     ListContactsResponse,
 )
@@ -52,14 +53,34 @@ def configure_contacts_tools(mcp: FastMCP):
         """List all contacts in the specified addressbook."""
         client = await get_client(ctx)
         contacts_data = await client.contacts.list_contacts(addressbook=addressbook)
-        contacts = [
-            Contact(
-                uid=c["vcard_id"],
-                fn=c.get("contact", {}).get("fullname", ""),
-                etag=c.get("getetag"),
+        contacts = []
+        for c in contacts_data:
+            contact_info = c.get("contact", {})
+
+            # Convert email field (str, list, or None) to list[ContactField]
+            raw_email = contact_info.get("email")
+            emails: list[ContactField] = []
+            if isinstance(raw_email, list):
+                emails = [ContactField(type="email", value=e) for e in raw_email if e]
+            elif isinstance(raw_email, str) and raw_email:
+                emails = [ContactField(type="email", value=raw_email)]
+
+            # Nickname goes into custom_fields (no dedicated model field)
+            custom_fields: dict[str, str] = {}
+            nickname = contact_info.get("nickname")
+            if nickname:
+                custom_fields["nickname"] = nickname
+
+            contacts.append(
+                Contact(
+                    uid=c["vcard_id"],
+                    fn=contact_info.get("fullname", ""),
+                    etag=c.get("getetag"),
+                    birthday=contact_info.get("birthday"),
+                    emails=emails,
+                    custom_fields=custom_fields,
+                )
             )
-            for c in contacts_data
-        ]
         return ListContactsResponse(
             contacts=contacts, addressbook=addressbook, total_count=len(contacts)
         )