Add extensive form tests and enhanced error handling for auth components.

- Introduced comprehensive tests for `RegisterForm`, `PasswordResetRequestForm`, and `PasswordResetConfirmForm` covering successful submissions, validation errors, and API error handling.
- Refactored forms to handle unexpected errors gracefully and improve test coverage for edge cases.
- Updated `crypto` and `storage` modules with robust error handling for storage issues and encryption key management.
- Removed unused `axios-mock-adapter` dependency for cleaner dependency management.

frontend/src/config/app.config.ts

@@ -132,6 +132,7 @@ export type AppConfig = typeof config;
  * Validate critical configuration on module load
  * Note: Most auth config validation is handled by parseIntSafe min/max constraints
  */
+/* istanbul ignore next - Browser-only validation, runs at build/startup time */
 function validateConfig(): void {
   const errors: string[] = [];