Fix cloud mode: ERB secrets, Redis auth, and Redis URL

- secrets.rb: Process ERB tags in secrets.yml and use ||= to not
  overwrite existing ENV vars (was clobbering SERVER_MODE=cloud with
  literal ERB string, causing app to fall into 'application' mode
  and redirect to /en/activate)
- license.rb: Use ENV['REDIS_URL'] for all Redis.new calls instead
  of defaulting to localhost (infrastructure Redis requires auth)
- redis.yml: Use ERB to read REDIS_URL env var for production
- sidekiq.rb: Process ERB when loading redis.yml

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/initializers/secrets.rb

@@ -1,6 +1,6 @@
-config = YAML.load_file("#{Rails.root}/config/secrets.yml")
+config = YAML.load(ERB.new(File.read("#{Rails.root}/config/secrets.yml")).result)
 config.fetch(Rails.env, {}).each do |key, value|
-  ENV[key.upcase] = value.to_s
+  ENV[key.upcase] ||= value.to_s
 end
 
 # SECRETS_CONFIG = YAML.load_file("#{Rails.root}/config/secrets.yml")[Rails.env]