WIP: restore database migration system and improve error handling

- Restore runMigrations functionality for database schema migrations
- Remove indexedDBMigrationService.ts (was for IndexedDB to SQLite migration)
- Recreate migrationService.ts and db-sql/migration.ts for schema management
- Add proper TypeScript error handling with type guards in AccountViewView
- Fix CreateAndSubmitClaimResult property access in QuickActionBvcBeginView
- Remove LeafletMouseEvent from Vue components array (it's a type, not component)
- Add null check for UserNameDialog callback to prevent undefined assignment
- Implement extractErrorMessage helper function for consistent error handling
- Update router to remove database-migration route

The migration system now properly handles database schema evolution
across app versions, while the IndexedDB to SQLite migration service
has been removed as it was specific to that one-time migration.

src/db/index.ts

@@ -1,7 +1,7 @@
 /**
  * This is the original IndexedDB version of the database.
  * It will eventually be replaced fully by the SQL version in databaseUtil.ts.
- * Turn this on or off with the USE_DEXIE_DB constant in constants/app.ts.
+ *
  */
 
 import BaseDexie, { Table } from "dexie";

src/db/tables/accounts.ts

@@ -45,7 +45,7 @@ export type Account = {
   publicKeyHex: string;
 };
 
-// When finished with USE_DEXIE_DB, move these fields to Account and move identity and mnemonic here.
+// TODO: When finished with USE_DEXIE_DB, move these fields to Account and move identity and mnemonic here.
 export type AccountEncrypted = Account & {
   identityEncrBase64: string;
   mnemonicEncrBase64: string;