feat: implement user authentication features (registration, activation, and password reset)

- Added email templates for activation and password reset (`activation_email.html`, `password_reset_email.html`, etc.)
- Created forms for registration (`RegisterForm`) and login (`LoginForm`) with custom validation
- Developed new pages for account activation (`activation_success.html`, `activation_invalid.html`), password reset workflow, and profile
- Configured email backend and environment file handling in settings
- Updated header template to conditionally display profile or login links based on authentication status
- Enhanced CSS styles for authentication-related pages and forms

templates/users/password_reset.html

@@ -0,0 +1,65 @@
+{% extends '_layouts/base.html' %}
+{% load static %}
+
+{% block title %}Сброс пароля{% endblock %}
+
+{% block add_css %}
+    <link rel="stylesheet" href="{% static 'css/login.css' %}">
+{% endblock %}
+
+{% block content %}
+    <div class="auth-page">
+        {% include "_fragments/header.html" %}
+
+        <main class="auth-section">
+            <div class="container auth-layout">
+                <section class="auth-intro auth-intro--reset">
+                    <p class="auth-kicker">Восстановление доступа</p>
+                    <h1 id="password-reset-title" class="auth-title">Сброс пароля</h1>
+                    <p class="auth-description">
+                        Укажите электронную почту, и мы отправим инструкции для восстановления доступа к вашему аккаунту.
+                    </p>
+                    <a class="auth-side-link" href="/users/login/">Вернуться ко входу</a>
+                </section>
+
+                <section class="auth-panel" aria-labelledby="password-reset-title">
+                    <form class="auth-form" action="" method="post">
+                        {% csrf_token %}
+                        {% if form.non_field_errors %}
+                            <div class="auth-alert auth-alert--error">
+                                {% for error in form.non_field_errors %}
+                                    <p>{{ error }}</p>
+                                {% endfor %}
+                            </div>
+                        {% endif %}
+
+                        <div class="auth-field">
+                            <label for="{{ form.email.id_for_label }}">Электронная почта</label>
+                            <input
+                                id="{{ form.email.id_for_label }}"
+                                name="{{ form.email.html_name }}"
+                                type="email"
+                                value="{{ form.email.value|default:'' }}"
+                                placeholder="example@mail.ru"
+                                autocomplete="email"
+                            >
+                            {% for error in form.email.errors %}
+                                <p class="auth-field-error">{{ error }}</p>
+                            {% endfor %}
+                        </div>
+
+                        <div class="auth-actions">
+                            <button class="auth-submit" type="submit">Отправить письмо</button>
+                            <p class="auth-switch">
+                                Вспомнили пароль?
+                                <a href="{% url 'users:login' %}">Вернуться ко входу</a>
+                            </p>
+                        </div>
+                    </form>
+                </section>
+            </div>
+        </main>
+
+        {% include "_fragments/footer.html" %}
+    </div>
+{% endblock %}