feat: add system health diagnostics

backend/app/frontend/static/system-health.css

@@ -0,0 +1,139 @@
+.health-toolbar,
+.health-section-head {
+    display: flex;
+    align-items: flex-start;
+    justify-content: space-between;
+    gap: 16px;
+}
+
+.health-toolbar {
+    margin-bottom: 12px;
+}
+
+.health-toolbar h2,
+.health-toolbar p,
+.health-section h2,
+.health-section h3 {
+    margin-top: 0;
+}
+
+.health-toolbar p {
+    margin-bottom: 0;
+    color: var(--muted-text, #52606d);
+}
+
+.health-notice {
+    border-left: 4px solid #64748b;
+    background: #f1f5f9;
+    margin: 0 0 14px;
+    padding: 10px 12px;
+}
+
+.health-notice[data-state="partial"] {
+    border-left-color: #b45309;
+    background: #fff7ed;
+}
+
+.health-notice[data-state="error"] {
+    border-left-color: #b91c1c;
+    background: #fef2f2;
+}
+
+.health-section {
+    border-top: 1px solid #cbd5e1;
+    padding: 16px 0;
+}
+
+.health-columns,
+.health-integrity-grid,
+.health-facts {
+    display: grid;
+    gap: 14px;
+}
+
+.health-columns {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+}
+
+.health-integrity-grid {
+    grid-template-columns: repeat(3, minmax(0, 1fr));
+}
+
+.health-facts {
+    grid-template-columns: repeat(4, minmax(0, 1fr));
+    margin: 0;
+}
+
+.health-facts-compact {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+}
+
+.health-facts div {
+    min-width: 0;
+}
+
+.health-facts dt {
+    color: #52606d;
+    font-size: 0.78rem;
+    font-weight: 700;
+}
+
+.health-facts dd {
+    font-weight: 700;
+    margin: 3px 0 0;
+    overflow-wrap: anywhere;
+}
+
+.health-links {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 10px;
+}
+
+.health-links a:focus-visible,
+#healthRefresh:focus-visible {
+    outline: 3px solid #0f766e;
+    outline-offset: 3px;
+}
+
+.table-scroll {
+    overflow-x: auto;
+}
+
+.table-scroll table {
+    width: 100%;
+    border-collapse: collapse;
+}
+
+.table-scroll th,
+.table-scroll td {
+    border-bottom: 1px solid #dbe2e8;
+    padding: 7px 8px;
+    text-align: left;
+}
+
+@media (max-width: 900px) {
+    .health-integrity-grid,
+    .health-facts {
+        grid-template-columns: repeat(2, minmax(0, 1fr));
+    }
+}
+
+@media (max-width: 640px) {
+    .health-toolbar,
+    .health-section-head {
+        align-items: stretch;
+        flex-direction: column;
+    }
+
+    .health-columns,
+    .health-integrity-grid,
+    .health-facts,
+    .health-facts-compact {
+        grid-template-columns: 1fr;
+    }
+
+    #healthRefresh {
+        width: 100%;
+    }
+}