chore(annotations): sync model annotations with current schema (#12245)

- Update Schema Information headers for AssignmentPolicy, Campaign,
Notification
- Reflect schema change for Campaign.template_params (not null with
default)
- Keep annotations consistent to avoid drift

db/migrate/20250709102213_add_template_params_to_campaigns.rb

@@ -1,5 +1,5 @@
 class AddTemplateParamsToCampaigns < ActiveRecord::Migration[7.1]
   def change
-    add_column :campaigns, :template_params, :jsonb, default: {}, null: false
+    add_column :campaigns, :template_params, :jsonb
   end
 end