convert all remaining DB writes & reads to SQL (with successful registration & claim)

src/db/tables/accounts.ts

@@ -45,6 +45,7 @@ export type Account = {
   publicKeyHex: string;
 };
 
+// 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;