Implement /tags and /tag/id endpoints

public/css/style.css

@@ -135,6 +135,20 @@ nav {
   gap: 0 1rem;
 }
 
+/* 0.5rem padding compensates the unused 1rem gap at the end. */
+.gallery {
+  align-items: center;
+  gap: 1rem;
+  padding: 0 0.5rem;
+}
+
+.gallery-image {
+  max-height: 24rem;
+  max-width: 14rem;
+  height: 100%;
+  width: 100%;
+}
+
 .flex-c-horizontal {
   display: flex;
 }
@@ -150,6 +164,10 @@ nav {
   align-items: center;
 }
 
+.flex-c-wrap {
+  flex-wrap: wrap;
+}
+
 .flex-i-fullsize {
   flex: auto;
 }