feat: Add seed backup tracking with database migration

- Add hasBackedUpSeed boolean flag to Settings interface
- Create database migration 003_add_hasBackedUpSeed_to_settings
- Update SeedBackupView to set flag when user reveals seed phrase
- Modify DataExportSection to conditionally show notification dot
- Implement robust error handling for database operations

The notification dot on the "Backup Identifier Seed" button only
appears while the user hasn't backed up their seed phrase. Once they
visit SeedBackupView and click "Reveal my Seed Phrase", the setting
is persisted and the notification dot disappears.

src/db/tables/settings.ts

@@ -29,6 +29,7 @@ export type Settings = {
   finishedOnboarding?: boolean; // the user has completed the onboarding process
 
   firstName?: string; // user's full name, may be null if unwanted for a particular account
+  hasBackedUpSeed?: boolean; // tracks whether the user has backed up their seed phrase
   hideRegisterPromptOnNewContact?: boolean;
   isRegistered?: boolean;
   // imageServer?: string; // if we want to allow modification then we should make image functionality optional -- or at least customizable