feat: Update job detail and logs routes to return friendly pages instead of 404 errors

abogen/webui/templates/job_logs_missing.html

@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+
+{% block title %}Job Not Found{% endblock %}
+
+{% block content %}
+<section class="card logs-static">
+  <div class="card__title-row">
+    <div class="card__title">Job Not Found</div>
+  </div>
+  <p>This job no longer exists. It may have been deleted or the server was restarted.</p>
+  <p><a href="{{ url_for('main.index') }}" class="button button--primary">Return to Dashboard</a></p>
+</section>
+{% endblock %}