[fix] Add .git to Copier Template _exclude

What?

Add the .git directory to the _exclude list in copier.yml to prevent copying of Git history when generating new projects.

Why?

Generated projects currently inherit the template's Git history, which is undesired behaviour. Each new project should start with a clean Git history.

How?

Feature: Copier Template Git Exclusion
  As a template maintainer
  I want to exclude the .git directory from being copied
  So that new projects start with a clean Git history

  Scenario: Adding .git to Exclude List
    Given the existing copier.yml file
    When I add ".git" to the _exclude list
    Then the template should not copy Git history to new projects

Definition of Done

Add ".git" to _exclude list in copier.yml
Test template generation to verify Git history is not copied
Verify that new projects initialise with clean Git history
Update template documentation if needed

Breaking change? ⚠️ No - This is a bugfix that implements expected behaviour.