Add logging functionality to the dev panel

backend/templates/dev_panel.html

@@ -2,13 +2,36 @@
 
 {% block content %}
 
-<div class="content" id="dev_panel">
+<div class="content" id="dev-panel">
     <input type="button" class="button" id="test-toast" value="Test toast">
     <input type="button" class="button" id="test-modal-dialog" value="Test modal">
+
+    <div type="log">
+        <ul class="log-files">
+            {% for f in log.file_names().unwrap() %}
+                <li class="log-file"><a href="/dev_panel?log_file={{ f }}">{{ f }}</a></li>
+            {% endfor %}
+        </ul>
+        <div class="current-log-file">
+            {% match log.read_content(current_log_file) %}
+            {% when Ok(lines) %}
+                {% for l in lines %}
+                    <div class="
+                    {% if loop.index0 % 2 == 0 %}
+                        log-line-even
+                    {% else %}
+                        log-line-odd
+                    {% endif %}
+                    " >{{ l }}</div>
+                {% endfor %}
+            {% when Err(err) %}
+                Error reading log: {{ err }}
+            {% endmatch %}
+        </div>
+    </div>
 </div>
 
 <div id="hidden-templates">
-
     <div class="modal-test-message">
         This is a message.
     </div>