feat: add Logs tab with cursor-paginated search, level filters, and live tail

- Extend GET /api/v1/logs with cursor pagination, multi-level filtering,
  optional application scoping, and level count aggregation
- Add exchangeId, instanceId, application, mdc fields to log responses
- Refactor ClickHouseLogStore with keyset pagination (N+1 pattern)
- Add LogSearchRequest/LogSearchResponse core domain records
- Create LogSearchPageResponse wrapper DTO
- Add Logs as 4th content tab (Exchanges | Dashboard | Runtime | Logs)
- Implement LogSearch component with debounced search, level filter bar,
  expandable log entries, cursor pagination, and live tail mode
- Add cross-navigation: exchange header → logs, log tab → logs tab
- Update ClickHouseLogStoreIT with cursor, multi-level, cross-app tests

Closes: #104

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

ui/src/pages/LogsTab/LogEntry.module.css

@@ -0,0 +1,187 @@
+.entry {
+  border-bottom: 1px solid var(--border-subtle);
+  cursor: pointer;
+  transition: background 0.1s;
+}
+
+.entry:hover {
+  background: var(--bg-hover);
+}
+
+.expanded {
+  background: var(--bg-surface);
+}
+
+.row {
+  display: flex;
+  align-items: baseline;
+  gap: 8px;
+  padding: 6px 12px;
+  font-size: 12px;
+  font-family: var(--font-mono);
+  min-height: 28px;
+}
+
+.timestamp {
+  color: var(--text-muted);
+  white-space: nowrap;
+  flex-shrink: 0;
+}
+
+.level {
+  font-weight: 600;
+  white-space: nowrap;
+  flex-shrink: 0;
+  min-width: 40px;
+}
+
+.logger {
+  color: var(--text-muted);
+  white-space: nowrap;
+  flex-shrink: 0;
+  max-width: 180px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  font-size: 11px;
+}
+
+.message {
+  color: var(--text-primary);
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.chips {
+  display: flex;
+  gap: 4px;
+  flex-shrink: 0;
+}
+
+.chip {
+  font-size: 10px;
+  padding: 1px 6px;
+  border-radius: var(--radius-sm);
+  background: var(--bg-raised);
+  color: var(--text-secondary);
+  cursor: pointer;
+  font-family: var(--font-body);
+}
+
+.chip:hover {
+  background: var(--border);
+}
+
+.detail {
+  padding: 8px 12px 12px 60px;
+  font-size: 12px;
+}
+
+.detailGrid {
+  display: grid;
+  grid-template-columns: 70px 1fr;
+  gap: 2px 8px;
+  margin-bottom: 8px;
+}
+
+.detailLabel {
+  color: var(--text-muted);
+  font-size: 11px;
+}
+
+.detailValue {
+  color: var(--text-primary);
+  font-family: var(--font-mono);
+  font-size: 11px;
+  word-break: break-all;
+}
+
+.fullMessage {
+  color: var(--text-primary);
+  font-family: var(--font-mono);
+  font-size: 12px;
+  white-space: pre-wrap;
+  word-break: break-word;
+  margin-bottom: 8px;
+  padding: 8px;
+  background: var(--bg-deep);
+  border-radius: var(--radius-sm);
+}
+
+.stackTrace {
+  font-family: var(--font-mono);
+  font-size: 11px;
+  color: var(--error);
+  background: var(--bg-deep);
+  border-radius: var(--radius-sm);
+  padding: 8px;
+  margin: 8px 0;
+  overflow-x: auto;
+  white-space: pre;
+  max-height: 300px;
+  overflow-y: auto;
+}
+
+.mdcSection {
+  margin-top: 8px;
+}
+
+.mdcGrid {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 4px;
+  margin-top: 4px;
+}
+
+.mdcEntry {
+  display: flex;
+  gap: 2px;
+  font-size: 11px;
+  font-family: var(--font-mono);
+  background: var(--bg-deep);
+  border-radius: var(--radius-sm);
+  padding: 2px 6px;
+}
+
+.mdcKey {
+  color: var(--text-muted);
+}
+
+.mdcValue {
+  color: var(--text-primary);
+}
+
+.actions {
+  display: flex;
+  gap: 8px;
+  margin-top: 8px;
+}
+
+.actionBtn {
+  background: none;
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-sm);
+  padding: 4px 10px;
+  font-size: 11px;
+  color: var(--text-secondary);
+  cursor: pointer;
+  font-family: var(--font-body);
+}
+
+.actionBtn:hover {
+  background: var(--bg-hover);
+  color: var(--text-primary);
+}
+
+.linkBtn {
+  background: none;
+  border: none;
+  padding: 0;
+  color: var(--amber);
+  cursor: pointer;
+  font-family: var(--font-mono);
+  font-size: 11px;
+  text-decoration: underline;
+}