Add Sentry, Pino logs, and OTel spans on WS pipeline (M2).

Capture REST/WS/SSE errors in Sentry, emit structured pino logs with correlation IDs, and trace the book-tick pipeline to Sentry via OpenTelemetry.

Co-authored-by: Cursor <cursoragent@cursor.com>

.github/dependabot.yml

@@ -0,0 +1,18 @@
+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: "/"
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: npm
+    directory: "/web"
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly