major styling pass, artist list, and import processing improvements

app/templates/artist_list.html

@@ -0,0 +1,23 @@
+{% extends "layout.html" %}
+{% block title %}Artists{% endblock %}
+
+{% block content %}
+<h1 style="text-align:center; margin-top: 1rem;">Artists</h1>
+
+<div class="artist-grid">
+  {% for artist in artist_data %}
+    <a href="{{ url_for('main.artist_gallery', artist_name=artist.name) }}" class="artist-card-link">
+      <div class="artist-card">
+        <h3>{{ artist.name }}</h3>
+        <div class="artist-preview">
+          {% for image in artist.images %}
+            <div class="artist-thumb"
+                 style="background-image: url('{{ url_for('main.serve_image', filename=image.filepath | replace('/images/', '')) }}');">
+            </div>
+          {% endfor %}
+        </div>
+      </div>
+    </a>
+  {% endfor %}
+</div>
+{% endblock %}