feat: Voice channel creation Flow (#11775)

This PR introduces a new channel type for voice conversations.

ref: #11481 

## Changes

- Add database migration for channel_voice table with phone_number and
provider_config
- Create Channel::Voice model with E.164 phone number validation and
Twilio config validation
- Add voice channel association to Account model
- Extend inbox helpers and types to support voice channels
- Add voice channel setup UI with Twilio configuration form
- Include voice channel in channel factory and list components
- Add API routes and store actions for voice channel creation
- Add comprehensive translations for voice channel management

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

db/migrate/20250620120000_create_channel_voice.rb

@@ -0,0 +1,16 @@
+class CreateChannelVoice < ActiveRecord::Migration[7.0]
+  def change
+    create_table :channel_voice do |t|
+      t.string :phone_number, null: false
+      t.string :provider, null: false, default: 'twilio'
+      t.jsonb :provider_config, null: false
+      t.integer :account_id, null: false
+      t.jsonb :additional_attributes, default: {}
+
+      t.timestamps
+    end
+
+    add_index :channel_voice, :phone_number, unique: true
+    add_index :channel_voice, :account_id
+  end
+end