feat: add Google Contacts (People API) support

Add 16 MCP tools for managing Google Contacts via the People API:

Core tier:
- list_contacts, get_contact, search_contacts, create_contact

Extended tier:
- update_contact, delete_contact, list_contact_groups, get_contact_group

Complete tier:
- batch_create_contacts, batch_update_contacts, batch_delete_contacts
- create_contact_group, update_contact_group, delete_contact_group
- modify_contact_group_members

Includes:
- OAuth scopes for contacts and contacts.readonly
- People API service configuration
- Tool tier definitions
- Unit tests for helper functions

main.py

@@ -103,6 +103,7 @@ def main():
             "forms",
             "slides",
             "tasks",
+            "contacts",
             "search",
             "appscript",
         ],
@@ -200,6 +201,7 @@ def main():
         "forms": lambda: import_module("gforms.forms_tools"),
         "slides": lambda: import_module("gslides.slides_tools"),
         "tasks": lambda: import_module("gtasks.tasks_tools"),
+        "contacts": lambda: import_module("gcontacts.contacts_tools"),
         "search": lambda: import_module("gsearch.search_tools"),
         "appscript": lambda: import_module("gappsscript.apps_script_tools"),
     }
@@ -214,6 +216,7 @@ def main():
         "forms": "📝",
         "slides": "🖼️",
         "tasks": "✓",
+        "contacts": "👤",
         "search": "🔍",
         "appscript": "📜",
     }