style: add CSS modules to all pages matching design system mock layouts

Replace inline styles with semantic CSS module classes for proper visual
structure: card wrappers with borders/shadows, grid layouts for stat
strips and charts, section headers, and typography classes.

Pages updated: Dashboard, ExchangeDetail, RoutesMetrics, AgentHealth,
AgentInstance.

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

ui/src/pages/Dashboard/Dashboard.module.css

@@ -0,0 +1,84 @@
+.healthStrip {
+  display: grid;
+  grid-template-columns: repeat(5, 1fr);
+  gap: 10px;
+  margin-bottom: 16px;
+}
+
+.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);
+}
+
+.tableRight {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+
+.tableMeta {
+  font-size: 11px;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.panelSection {
+  padding-bottom: 16px;
+  margin-bottom: 16px;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.panelSection:last-child {
+  border-bottom: none;
+  margin-bottom: 0;
+  padding-bottom: 0;
+}
+
+.panelSectionTitle {
+  font-size: 11px;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
+  color: var(--text-muted);
+  margin-bottom: 10px;
+}
+
+.overviewGrid {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.overviewRow {
+  display: flex;
+  align-items: flex-start;
+  gap: 12px;
+}
+
+.overviewLabel {
+  font-size: 10px;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.6px;
+  color: var(--text-muted);
+  width: 90px;
+  flex-shrink: 0;
+  padding-top: 2px;
+}