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/tools/__init__.py

@@ -21,6 +21,14 @@ from .package_query import (
     query_package_info,
     query_package_versions,
 )
+from .publishing import (
+    check_pypi_credentials,
+    delete_pypi_release,
+    get_pypi_account_info,
+    get_pypi_upload_history,
+    manage_pypi_maintainers,
+    upload_package_to_pypi,
+)
 from .search import (
     find_alternatives,
     get_trending_packages,
@@ -44,4 +52,10 @@ __all__ = [
     "search_by_category",
     "find_alternatives",
     "get_trending_packages",
+    "upload_package_to_pypi",
+    "check_pypi_credentials",
+    "get_pypi_upload_history",
+    "delete_pypi_release",
+    "manage_pypi_maintainers",
+    "get_pypi_account_info",
 ]