Implement PyPI Account & Publishing Tools

Add comprehensive PyPI publishing and account management functionality:

Features:
- upload_package_to_pypi: Upload distributions to PyPI/TestPyPI with safety checks
- check_pypi_credentials: Validate API tokens and credentials
- get_pypi_upload_history: View upload history for packages with statistics
- delete_pypi_release: Safe release deletion with dry-run and confirmation
- manage_pypi_maintainers: Add/remove/list package maintainers
- get_pypi_account_info: View account details, quotas, and limits

Implementation:
- Created pypi_query_mcp/tools/publishing.py with all 6 functions
- Added PyPIPublishingClient for authenticated API operations
- Comprehensive error handling with custom exceptions
- Full async/await patterns following existing codebase conventions
- Safety checks for destructive operations (deletion requires confirmation)
- Support for both production PyPI and TestPyPI

Integration:
- Added publishing-specific exceptions to core/exceptions.py
- Updated tools/__init__.py with publishing function imports
- Added 6 MCP server endpoints to server.py with proper error handling
- Created comprehensive tests in tests/test_publishing.py

Production-ready code with proper authentication, validation, and safety measures.

pypi_query_mcp/core/exceptions.py

@@ -62,3 +62,24 @@ class SearchError(PyPIError):
     def __init__(self, message: str, query: str | None = None):
         super().__init__(message)
         self.query = query
+
+
+class PyPIAuthenticationError(PyPIError):
+    """Raised when PyPI authentication fails."""
+    
+    def __init__(self, message: str, status_code: int | None = None):
+        super().__init__(message, status_code)
+
+
+class PyPIUploadError(PyPIError):
+    """Raised when PyPI upload operations fail."""
+    
+    def __init__(self, message: str, status_code: int | None = None):
+        super().__init__(message, status_code)
+
+
+class PyPIPermissionError(PyPIError):
+    """Raised when PyPI permission operations fail."""
+    
+    def __init__(self, message: str, status_code: int | None = None):
+        super().__init__(message, status_code)