Normalize disappearing settings bearer tokens

[aiirvizionz]

Summary

• normalize disappearing-message settings Bearer headers with case-insensitive scheme handling and whitespace trimming
• reject empty Bearer headers before creating the service-role client
• cover GET and PUT auth parsing with focused route tests

Tests

• vitest run src/app/api/settings/disappearing-messages/route.test.js
• node --check src/app/api/settings/disappearing-messages/route.js
• node --check src/app/api/settings/disappearing-messages/route.test.js
• git diff --check