Add admin panel, WebSocket support, and API versioning

Introduce an admin portal (React + Nginx), WebSocket routing, and
API versioning middleware with `/api/v1/` prefix deprecation.
Add master API key authentication, new Prometheus metrics for AI
token consumption and active WebSockets, and extend S3 config
with a public endpoint URL. Update test paths and fixtures to
align with the new routing structure.

integration/shaarli/config_example.env

@@ -0,0 +1,11 @@
+# Imago Hub API Connection details
+IMAGO_API_URL=http://localhost:8000/api/v1
+IMAGO_API_KEY=your-shaarli-client-api-key-here
+
+# Shaarli API credentials (if Imago needs to call back to Shaarli)
+SHAARLI_API_URL=https://bookmarks.example.com/api/v1
+SHAARLI_API_SECRET=your-shaarli-api-secret
+
+# Plugin configuration
+PLUGIN_ENABLE_AI_SUMMARIZATION=true
+PLUGIN_ENABLE_IMAGE_UPLOAD=true