Refactor extension handlers and improve mobile UX

- Split extensionMessageHandler into separate handler files
  - Created handlers directory with individual files for database, filesystem, http, permissions, context, and storage
  - Reduced main handler file from 602 to 342 lines
  - Improved code organization and maintainability

- Add viewport utilities for safe area handling
  - New viewport.ts utility with helpers for fullscreen dimensions
  - Proper safe area inset calculations for mobile devices
  - Fixed window positioning on small screens to start at 0,0

- Create UiDrawer wrapper component
  - Automatically applies safe area insets
  - Uses TypeScript DrawerProps interface for code completion
  - Replaced all UDrawer instances with UiDrawer

- Improve window management
  - Windows on small screens now use full viewport with safe areas
  - Fixed maximize functionality to respect safe areas
  - Consolidated safe area logic in reusable utilities

src/composables/handlers/index.ts

@@ -0,0 +1,10 @@
+// Export all handler functions
+export { handleDatabaseMethodAsync } from './database'
+export { handleFilesystemMethodAsync } from './filesystem'
+export { handleHttpMethodAsync } from './http'
+export { handlePermissionsMethodAsync } from './permissions'
+export { handleContextMethodAsync, setContextGetters } from './context'
+export { handleStorageMethodAsync } from './storage'
+
+// Export shared types
+export type { ExtensionRequest, ExtensionInstance } from './types'