Remove Flipper and replace with ENV-driven FeatureFlags (#957)

* Presence of valid DEFAULT_UI_LAYOUT is sufficient

* Linter

app/services/provider_loader.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Service class to load SSO provider configurations from either YAML or database
-# based on the :db_sso_providers feature flag.
+# based on the AUTH_PROVIDERS_SOURCE environment setting.
 #
 # Usage:
 #   providers = ProviderLoader.load_providers
@@ -38,17 +38,7 @@ class ProviderLoader
       def use_database_providers?
         return false if Rails.env.test?
 
-        begin
-          # Check if feature exists, create if not (defaults to disabled)
-          unless Flipper.exist?(:db_sso_providers)
-            Flipper.add(:db_sso_providers)
-          end
-          Flipper.enabled?(:db_sso_providers)
-        rescue ActiveRecord::NoDatabaseError, ActiveRecord::StatementInvalid, StandardError => e
-          # Database not ready or other error, fall back to YAML
-          Rails.logger.warn("[ProviderLoader] Could not check feature flag (#{e.class}), falling back to YAML providers")
-          false
-        end
+        FeatureFlags.db_sso_providers?
       end
 
       def load_from_database

app/views/admin/sso_providers/index.html.erb

@@ -3,7 +3,7 @@
 <div class="space-y-4">
   <p class="text-secondary mb-4">
     Manage single sign-on authentication providers for your instance.
-    <% unless Flipper.enabled?(:db_sso_providers) %>
+    <% unless FeatureFlags.db_sso_providers? %>
       <span class="text-warning">Changes require a server restart to take effect.</span>
     <% end %>
   </p>
@@ -107,7 +107,7 @@
           <p class="font-medium text-primary">Database-backed providers</p>
           <p class="text-sm text-secondary">Load providers from database instead of YAML config</p>
         </div>
-        <% if Flipper.enabled?(:db_sso_providers) %>
+        <% if FeatureFlags.db_sso_providers? %>
           <span class="inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-green-100 text-green-800">
             Enabled
           </span>

app/views/invitations/new.html.erb

@@ -10,7 +10,7 @@
 
       <%= form.select :role,
         options_for_select([
-          (Flipper.enabled?(:intro_ui) ? [t(".role_guest"), "guest"] : nil),
+          (FeatureFlags.intro_ui? ? [t(".role_guest"), "guest"] : nil),
           [t(".role_member"), "member"],
           [t(".role_admin"), "admin"]
         ].compact),