feat: extract shared infrastructure from shared_lib

Phase 1-3 of decoupling plan:
- Shared DB, models, infrastructure, browser, config, utils
- Event infrastructure (domain_events outbox, bus, processor)
- Structured logging
- Generic container concept (container_type/container_id)
- Alembic migrations for all schema changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

browser/templates/sentinel/desktop_content.html

@@ -0,0 +1,9 @@
+<div class="js-loading text-center text-xs text-stone-400">
+    loading… {{ page }} / {{ total_pages }}
+  </div>
+
+   <div class="js-neterr hidden inset-0 grid place-items-center p-4">
+    <div class="w-full max-w-[360px]">
+      {% include "sentinel/wireless_error.svg" %}
+    </div>
+  </div>