Add QA evidence map overlay

frontend/src/styles/app.css

@@ -2564,11 +2564,81 @@ button.entity-card {
 
 .layer-provenance-rail {
   display: grid;
-  grid-template-columns: 0.85fr minmax(0, 1.5fr) 0.85fr;
+  grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr));
   gap: 0.65rem;
   margin-bottom: 0;
 }
 
+.qa-evidence-map-status {
+  display: grid;
+  grid-template-columns: minmax(0, 1.2fr) minmax(0, 1.6fr) auto;
+  gap: 0.65rem;
+  align-items: center;
+  border: 1px solid #bfdbfe;
+  border-left: 4px solid #2563eb;
+  border-radius: 8px;
+  padding: 0.72rem;
+  background: #eff6ff;
+}
+
+.qa-evidence-map-status span,
+.qa-evidence-map-status strong {
+  display: block;
+}
+
+.qa-evidence-map-status > div:first-child span {
+  color: #1d4ed8;
+  font-size: 0.68rem;
+  font-weight: 850;
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
+}
+
+.qa-evidence-map-status > div:first-child strong {
+  margin-top: 0.18rem;
+  color: #172554;
+}
+
+.qa-evidence-legend {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(8.5rem, 1fr));
+  gap: 0.38rem;
+}
+
+.qa-evidence-legend span {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.38rem;
+  color: #1e3a8a;
+  font-size: 0.78rem;
+  font-weight: 750;
+}
+
+.qa-evidence-swatch {
+  display: inline-block;
+  width: 0.72rem;
+  height: 0.72rem;
+  border-radius: 999px;
+  border: 2px solid #ffffff;
+  box-shadow: 0 0 0 1px rgba(15, 23, 42, 0.18);
+}
+
+.qa-evidence-swatch-match-candidate {
+  background: #2563eb;
+}
+
+.qa-evidence-swatch-match-reference {
+  background: #0f766e;
+}
+
+.qa-evidence-swatch-false-positive {
+  background: #dc2626;
+}
+
+.qa-evidence-swatch-false-negative {
+  background: #d97706;
+}
+
 .layer-provenance-rail > div,
 .feature-property-chip {
   min-width: 0;