implement login + logout routes and templates

+ Added route: GET `/login` via `aurweb.routers.auth.login_get`
+ Added route: POST `/login` via `aurweb.routers.auth.login_post`
+ Added route: GET `/logout` via `aurweb.routers.auth.logout`
+ Added route: POST `/logout` via `aurweb.routers.auth.logout_post`
* Modify archdev-navbar.html template to toggle displays on auth state
+ Added login.html template

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/partials/archdev-navbar.html

@@ -1,8 +1,22 @@
 <div id="archdev-navbar">
     <ul>
-        <li><a href="/">AUR {% trans %}Home{% endtrans %}</a></li>
+        {% if request.user.is_authenticated() %}
+            <li><a href="/">{% trans %}Dashboard{% endtrans %}</a></li>
+        {% else %}
+            <li><a href="/">AUR {% trans %}Home{% endtrans %}</a></li>
+        {% endif %}
         <li><a href="/packages/">{% trans %}Packages{% endtrans %}</a></li>
         <li><a href="/register/">{% trans %}Register{% endtrans %}</a></li>
-        <li><a href="/login/">{% trans %}Login{% endtrans %}</a></li>
+        <li>
+            {% if request.user.is_authenticated() %}
+                <a href="/logout/?next={{ next }}">
+                    {% trans %}Logout{% endtrans %}
+                </a>
+            {% else %}
+                <a href="/login/?next={{ next }}">
+                    {% trans %}Login{% endtrans %}
+                </a>
+            {% endif %}
+        </li>
     </ul>
 </div>