Add support for custom configuration file path in TemplateServer

[javidahmed64592]

This pull request refactors the configuration loading mechanism in TemplateServer to improve flexibility and clarity. The main change is that the server now accepts a full configuration file path, rather than just a filename, which enhances configurability and testability. Related tests have been updated to reflect this new behavior.

Configuration loading improvements:

• The TemplateServer constructor now takes a config_filepath parameter (defaulting to CONFIG_DIR / CONFIG_FILE_NAME) instead of just a filename, allowing users to specify the full path to the configuration file. (python_template_server/template_server.py)
• The load_config method now requires a Path object for the configuration file path, and all references within the method have been updated to use this parameter, improving clarity and error messaging. (python_template_server/template_server.py)
• The initialization logic in TemplateServer.__init__ now calls load_config(config_filepath) instead of load_config(), ensuring the correct path is used. (python_template_server/template_server.py)

Testing updates:

• Added and updated tests to verify that load_config is called with the specified file path and that the configuration is loaded as expected. (tests/test_template_server.py)
• Imports in the test file were updated to include Path for consistency with the new parameter type. (tests/test_template_server.py)