fix(sla): freeze misses after resolution

db/migrate/20260715000000_add_completed_at_to_applied_slas.rb

@@ -0,0 +1,5 @@
+class AddCompletedAtToAppliedSlas < ActiveRecord::Migration[7.1]
+  def change
+    add_column :applied_slas, :completed_at, :datetime
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2026_07_13_184351) do
+ActiveRecord::Schema[7.1].define(version: 2026_07_15_000000) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -178,6 +178,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_07_13_184351) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "sla_status", default: 0
+    t.datetime "completed_at"
     t.index ["account_id", "sla_policy_id", "conversation_id"], name: "index_applied_slas_on_account_sla_policy_conversation", unique: true
     t.index ["account_id"], name: "index_applied_slas_on_account_id"
     t.index ["conversation_id"], name: "index_applied_slas_on_conversation_id"