feat: Added Instagram channel migration (#11181)

This PR is part of https://github.com/chatwoot/chatwoot/pull/11054 to
make the review cycle easier.

db/migrate/20250326034635_add_instagram_channel.rb

@@ -0,0 +1,13 @@
+class AddInstagramChannel < ActiveRecord::Migration[7.0]
+  def change
+    create_table :channel_instagram do |t|
+      t.string :access_token, null: false
+      t.datetime :expires_at, null: false
+      t.integer :account_id, null: false
+      t.string :instagram_id, null: false
+      t.timestamps
+    end
+
+    add_index :channel_instagram, :instagram_id, unique: true
+  end
+end