Add generateSecureBase58Token to shared utils with login_ prefix

- Create packages/utils/src/generate-base58-token.ts with typed prefix support
- Function returns `${TPrefix}${string}` for type-safe prefixed tokens
- Add isBase58() validator and parseBase58Token() helper
- Add comprehensive tests (13 test cases)

- Update login request tokens to use "login_" prefix
- Fix login-password.ts to not replace token (cookie/DB mismatch bug)
- Migrate all token generation from generateSecureToken (hex) to
  generateSecureBase58Token (base58)
- Remove duplicate token generation from api-server/utils/crypto.ts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/utils/src/index.ts

@@ -1 +1,6 @@
+export {
+  generateSecureBase58Token,
+  isBase58,
+  parseBase58Token,
+} from "./generate-base58-token.js";
 export { hashPassword, verifyPassword } from "./hash-password.js";