Refactor elimination feature and improve backoffice usability

This commit introduces a refactored EliminationFactory for better modularity, updates the elimination preparation process, and adds functionality to view eliminations. Backoffice templates and forms have been reorganized, minor translations were corrected, and additional assets like styles and flashes were included for enhanced user experience.

templates/backoffice/login/login.html.twig

@@ -0,0 +1,41 @@
+{% extends 'backoffice/base.html.twig' %}
+
+{% block title %}Log in{% endblock %}
+
+{% block body %}
+    {% if app.user %}
+        <div class="mb-3">
+            You are logged in as {{ app.user.userIdentifier }}, <a href="{{ path('app_login_logout') }}">Logout</a>
+        </div>
+    {% else %}
+        <form method="post">
+            <h1 class="py-2 h3 mb-3 font-weight-normal">{{ 'Please sign in'|trans }}</h1>
+            <div class="mb-3">
+                <label for="username" class="form-label">{{ 'Email'|trans }}</label>
+                <input type="email" value="{{ last_username }}" name="_username" id="username" class="form-control"
+                       autocomplete="email" required autofocus>
+            </div>
+
+            <div class="mb-3">
+                <label for="password" class="form-label">{{ 'Password'|trans }}</label>
+                <input type="password" name="_password" id="password" class="form-control"
+                       autocomplete="current-password"
+                       required>
+            </div>
+
+            <input type="hidden" name="_csrf_token" data-controller="csrf-protection"
+                   value="{{ csrf_token('authenticate') }}">
+
+            <div class="mb-3 form-check">
+                <input type="checkbox" name="_remember_me" id="_remember_me" class="form-check-input">
+                <label for="_remember_me" class="form-check-label">{{ 'Remember me'|trans }}</label>
+            </div>
+
+            <button class="btn btn-lg btn-primary" type="submit">
+                {{ 'Sign in'|trans }}
+            </button>
+            <a href="{{ path('app_register') }}"
+               class="btn btn-link">{{ 'Create an account'|trans }}</a>
+        </form>
+    {% endif %}
+{% endblock %}