Fix linting issues and update API key test for source validation

- Remove trailing whitespace in auth controller and mobile device model
- Update API key test to expect new validation message with source

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/controllers/api/v1/auth_controller.rb

@@ -175,7 +175,7 @@ module Api
         def create_or_update_device(user)
           # Handle both string and symbol keys
           device_data = params[:device].permit(:device_id, :device_name, :device_type, :os_version, :app_version)
-          
+
           device = user.mobile_devices.find_or_initialize_by(device_id: device_data[:device_id])
           device.update!(device_data.merge(last_seen_at: Time.current))
           device

app/models/mobile_device.rb

@@ -27,7 +27,7 @@ class MobileDevice < ApplicationRecord
       scopes: "read_write", # Use the configured scope
       confidential: false # Public client for mobile
     )
-    
+
     # Store the association
     update!(oauth_application: app)
     app
@@ -35,7 +35,7 @@ class MobileDevice < ApplicationRecord
 
   def active_tokens
     return Doorkeeper::AccessToken.none unless oauth_application
-    
+
     Doorkeeper::AccessToken
       .where(application: oauth_application)
       .where(resource_owner_id: user_id)