Add global recent-deployments feed for the projects dashboard

The RECENT DEPLOYMENTS section queried the builds table, so
image-sourced services — which deploy without building — never
appeared and the dashboard reported "no deployments yet" while
containers were running.

- GET /api/v1/deployments lists latest deployments across the
  caller's services, joined with service + project names, ordered
  newest-first with a bounded limit
- ProjectsPage consumes it via listRecentDeployments; the DEPLOYS
  stat card now counts real deployments
- is_admin is now projected in register/upsert user responses, and
  the Better Auth mirror grants admin to the first mirrored account
  (previously only the legacy register path did)

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/routes.go

@@ -219,6 +219,7 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			// Deployment routes
 			protected.GET("/services/:id/deployments", handleGetDeployments)
 			protected.POST("/services/:id/deployments", handleCreateDeployment)
+			protected.GET("/deployments", handleGetRecentDeployments)
 			protected.GET("/deployments/:id", handleGetDeployment)
 			protected.POST("/deployments/:id/rollback", handleRollbackDeployment)