add setup onboarding page, dashboard launch checklist, provider registry

- new /setup page with three-section onboarding (account, provider, payments)
- dashboard launch checklist with progress bar, go-live, dismiss
- provider registry on Provider module (single source of truth for metadata)
- payments registry for Stripe
- setup context made provider-agnostic (provider_connected, theme_customised, etc.)
- admin provider pages now fully registry-driven (no hardcoded provider names)
- auth flow: fresh installs redirect to /setup, signed_in_path respects setup state
- removed old /admin/setup wizard
- 840 tests, 0 failures

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

lib/berrypod_web/live/admin/providers/index.html.heex

@@ -6,11 +6,8 @@
         <.icon name="hero-plus" class="size-4 mr-1" /> Connect provider
       </div>
       <ul tabindex="0" class="admin-dropdown-content">
-        <li>
-          <.link navigate={~p"/admin/providers/new?type=printify"}>Printify</.link>
-        </li>
-        <li>
-          <.link navigate={~p"/admin/providers/new?type=printful"}>Printful</.link>
+        <li :for={provider <- @available_providers}>
+          <.link navigate={~p"/admin/providers/new?type=#{provider.type}"}>{provider.name}</.link>
         </li>
       </ul>
     </div>
@@ -22,15 +19,14 @@
     <.icon name="hero-cube" class="size-16 mx-auto mb-4 text-base-content/30" />
     <h2 class="text-xl font-medium">Connect a print-on-demand provider</h2>
     <p class="mt-2 text-base-content/60 max-w-md mx-auto">
-      Connect your Printify or Printful account to import products
-      and start selling.
+      Connect your account to import products and start selling.
     </p>
     <div class="flex justify-center gap-3 mt-6">
-      <.button navigate={~p"/admin/providers/new?type=printify"}>
-        Connect Printify
-      </.button>
-      <.button navigate={~p"/admin/providers/new?type=printful"} variant="outline">
-        Connect Printful
+      <.button
+        :for={provider <- @available_providers}
+        navigate={~p"/admin/providers/new?type=#{provider.type}"}
+      >
+        Connect {provider.name}
       </.button>
     </div>
   </div>
@@ -46,7 +42,7 @@
           <div class="flex items-center gap-2">
             <.status_indicator status={connection.sync_status} enabled={connection.enabled} />
             <h3 class="font-semibold text-lg">
-              {String.capitalize(connection.provider_type)}
+              {provider_name(connection.provider_type)}
             </h3>
           </div>
           <p class="text-base-content/70 mt-1">{connection.name}</p>
@@ -65,7 +61,7 @@
           <button
             phx-click="delete"
             phx-value-id={connection.id}
-            data-confirm={"Disconnect from #{String.capitalize(connection.provider_type)}? Your synced products will remain in your shop."}
+            data-confirm={"Disconnect from #{provider_name(connection.provider_type)}? Your synced products will remain in your shop."}
             class="admin-btn admin-btn-ghost admin-btn-sm text-error"
           >
             Disconnect