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/mobile_content.html

@@ -0,0 +1,11 @@
+ <!-- tiny loading text (default) -->
+  <div class="js-loading text-center text-xs text-stone-400">
+    loading… {{ page }} / {{ total_pages }}
+  </div>
+
+  <!-- BIG error panel (hidden by default) -->
+  <div class="js-neterr hidden flex h-full items-center justify-center">
+    <!-- Funky SVG: unplugged cable + pulse -->
+
+    {% include "sentinel/wireless_error.svg" %}
+  </div>