feat: progressive drill-down dashboard with RED metrics and SLA compliance (#94)

Three-level dashboard driven by sidebar selection:
- L1 (no selection): all-apps overview with health table, per-app charts
- L2 (app selected): route performance table, error velocity, top errors
- L3 (route selected): processor table, latency heatmap data, bottleneck KPI

Backend: 3 new endpoints (timeseries/by-app, timeseries/by-route, errors/top),
per-app SLA settings (app_settings table, V12 migration), exact SLA compliance
from executions hypertable, error velocity with acceleration detection.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/DashboardTab/DashboardTab.module.css

@@ -0,0 +1,133 @@
+.content {
+  display: flex;
+  flex-direction: column;
+  gap: 20px;
+}
+
+.refreshIndicator {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  justify-content: flex-end;
+}
+
+.refreshDot {
+  width: 7px;
+  height: 7px;
+  border-radius: 50%;
+  background: var(--success);
+  box-shadow: 0 0 4px rgba(61, 124, 71, 0.5);
+  animation: pulse 2s ease-in-out infinite;
+}
+
+@keyframes pulse {
+  0%, 100% { opacity: 1; }
+  50% { opacity: 0.5; }
+}
+
+.refreshText {
+  font-size: 11px;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+/* Tables */
+.tableSection {
+  background: var(--bg-surface);
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-lg);
+  box-shadow: var(--shadow-card);
+  overflow: hidden;
+}
+
+.tableHeader {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 12px 16px;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.tableTitle {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-primary);
+}
+
+.tableMeta {
+  font-size: 11px;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+/* Charts */
+.chartGrid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 16px;
+}
+
+.chartRow {
+  display: grid;
+  grid-template-columns: 1fr 1fr 1fr;
+  gap: 16px;
+}
+
+/* Cells */
+.monoCell {
+  font-size: 12px;
+  font-family: var(--font-mono);
+  color: var(--text-primary);
+}
+
+.appNameCell {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 12px;
+  font-weight: 500;
+  color: var(--text-primary);
+  font-family: var(--font-mono);
+  cursor: pointer;
+}
+
+.appNameCell:hover {
+  text-decoration: underline;
+}
+
+/* Rate coloring */
+.rateGood { color: var(--success); }
+.rateWarn { color: var(--warning); }
+.rateBad { color: var(--error); }
+.rateNeutral { color: var(--text-secondary); }
+
+/* Diagram container */
+.diagramSection {
+  background: var(--bg-surface);
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-lg);
+  box-shadow: var(--shadow-card);
+  overflow: hidden;
+  height: 280px;
+}
+
+/* Table right side (meta + badge) */
+.tableRight {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+
+/* Chart fill */
+.chart {
+  width: 100%;
+}
+
+/* Errors section */
+.errorsSection {
+  background: var(--bg-surface);
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-lg);
+  box-shadow: var(--shadow-card);
+  overflow: hidden;
+}