Add naive impl of seeding alerts

db/schema.rb

@@ -14,12 +14,14 @@ ActiveRecord::Schema[8.0].define(version: 2025_10_08_063847) do
   create_table "alerts", force: :cascade do |t|
     t.string "category", null: false
     t.text "description"
+    t.string "identifier", null: false
     t.string "park_code", null: false
     t.string "title", null: false
     t.string "url"
     t.datetime "indexed_date"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["identifier"], name: "index_alerts_on_identifier", unique: true
     t.index ["park_code"], name: "index_alerts_on_park_code"
   end