Redirects: properly redirect to the current week

Previously, most redirects targeted the root of the application.
This was okay for the first part of development where only one week would be
active, but would be annoying when using multiple weeks.

Change those redirects to call week::week.

Change the login path to be dependant on the current week as well,
so it can be correctly redirected.

templates/index.html.tera

@@ -42,7 +42,7 @@
     {% if user.logged_in == true %}
         <p>Connecté en tant que <b>{{ user.name }}</b></p>
     {% else %}
-        <form class="login" id="login" action="/login" method="POST">
+        <form class="login" id="login" action="/{{ week_data.number }}/login" method="POST">
             <label>Pseudo <input form="login" type="text" name="name"/></label>
             <label>Mot de passe <input form="login" type="password" name="password"/></label>
             <button form="login">Se connecter</button>