feat(web): add fan date range modes and delta column

reaction_board/web/static/style.css

@@ -531,6 +531,24 @@ h1, h2, h3, p { margin: 0; }
   .filter-row .select { width: 100%; max-width: none; }
 }
 .growth-days { padding-top: 2px; }
+.date-range {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 6px;
+  margin-top: 8px;
+}
+.date-range input[type="date"] {
+  min-height: 38px;
+  padding: 8px 11px;
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  background: var(--surface);
+  color: inherit;
+  font: inherit;
+  font-size: 13px;
+}
+.date-range span { color: var(--muted); font-size: 12px; }
 
 .rank-list { display: flex; flex-direction: column; gap: 8px; }
 .pager {
@@ -632,6 +650,7 @@ h1, h2, h3, p { margin: 0; }
 .data-table th { position: sticky; top: 0; background: var(--surface-2); color: var(--muted); font-size: 11px; font-weight: 600; }
 .data-table tr:last-child td { border-bottom: 0; }
 .data-table .failed-row td { color: var(--muted); background: color-mix(in srgb, var(--danger) 5%, transparent); }
+.fans-page .data-table { min-width: 0; }
 .summary-cell { max-width: 280px; overflow: hidden; text-overflow: ellipsis; }
 
 .hero-number {