feat: add service lock file and multi-worker startup guard with session cache clear

devplacepy/templates/_user_link.html

@@ -0,0 +1,5 @@
+{% if _user %}
+<a href="/profile/{{ _user['username'] }}"{% if _class %} class="{{ _class }}"{% endif %}>{{ _user['username'] }}</a>
+{% else %}
+<a href="#"{% if _class %} class="{{ _class }}"{% endif %}>Unknown</a>
+{% endif %}