add Oban Web dashboard at /admin/oban

Bump oban to 2.19+, add oban_web for real-time job monitoring.
Mounted behind admin auth with sidebar link under "Jobs".

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

lib/berrypod_web/router.ex

@@ -4,6 +4,7 @@ defmodule BerrypodWeb.Router do
   import BerrypodWeb.UserAuth
   import Phoenix.LiveDashboard.Router
   import ErrorTracker.Web.Router
+  import Oban.Web.Router
 
   pipeline :browser do
     plug :accepts, ["html"]
@@ -123,12 +124,13 @@ defmodule BerrypodWeb.Router do
     end
   end
 
-  # LiveDashboard and ErrorTracker behind admin auth (available in all environments)
+  # LiveDashboard, ErrorTracker, and Oban Web behind admin auth
   scope "/admin" do
     pipe_through [:browser, :require_authenticated_user]
 
     live_dashboard "/dashboard", metrics: BerrypodWeb.Telemetry
     error_tracker_dashboard("/errors")
+    oban_dashboard("/oban", resolver: BerrypodWeb.ObanResolver)
   end
 
   # Admin pages with sidebar layout