Simplify PushTarget by removing template method pattern

Each target now implements process directly with its own logic,
rather than using processable?/perform_push hooks. The pushable?
check is done once in Notification#push before iterating targets.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/models/notification/push_target/web_test.rb

@@ -37,20 +37,6 @@ class Notification::PushTarget::WebTest < ActiveSupport::TestCase
     Notification::PushTarget::Web.new(@notification).process
   end
 
-  test "does not push for cancelled accounts" do
-    @user.account.cancel(initiated_by: @user)
-    @web_push_pool.expects(:queue).never
-
-    Notification::PushTarget::Web.new(@notification).process
-  end
-
-  test "does not push when creator is system user" do
-    @notification.update!(creator: users(:system))
-    @web_push_pool.expects(:queue).never
-
-    Notification::PushTarget::Web.new(@notification).process
-  end
-
   test "payload includes card title for card events" do
     @web_push_pool.expects(:queue).once.with do |payload, _|
       payload[:title] == @notification.card.title

test/models/notification/pushable_test.rb

@@ -46,19 +46,43 @@ class Notification::PushableTest < ActiveSupport::TestCase
     Notification.push_targets = original_targets
   end
 
-  test "pushable? returns true for normal notifications" do
-    assert @notification.pushable?
+  test "push processes targets for normal notifications" do
+    target_class = mock("push_target_class")
+    target_class.expects(:process).with(@notification)
+
+    original_targets = Notification.push_targets
+    Notification.push_targets = [ target_class ]
+
+    @notification.push
+  ensure
+    Notification.push_targets = original_targets
   end
 
-  test "pushable? returns false when creator is system user" do
+  test "push skips targets when creator is system user" do
     @notification.update!(creator: users(:system))
 
-    assert_not @notification.pushable?
+    target_class = mock("push_target_class")
+    target_class.expects(:process).never
+
+    original_targets = Notification.push_targets
+    Notification.push_targets = [ target_class ]
+
+    @notification.push
+  ensure
+    Notification.push_targets = original_targets
   end
 
-  test "pushable? returns false for cancelled accounts" do
+  test "push skips targets for cancelled accounts" do
     @user.account.cancel(initiated_by: @user)
 
-    assert_not @notification.pushable?
+    target_class = mock("push_target_class")
+    target_class.expects(:process).never
+
+    original_targets = Notification.push_targets
+    Notification.push_targets = [ target_class ]
+
+    @notification.push
+  ensure
+    Notification.push_targets = original_targets
   end
 end