fix(web): unify password validation logic in RegisterPage (#943)

Remove duplicate password validation logic to ensure consistency.
Changes:
- Remove custom isStrongPassword function (RegisterPage.tsx:569-576)
- Use PasswordChecklist validation result (passwordValid state) instead
- Add comprehensive test suite with 28 test cases
- Configure Vitest with jsdom environment and setup file
Test Coverage:
- Password validation rules (length, uppercase, lowercase, number, special chars)
- Special character consistency (/[@#$%!&*?]/)
- Edge cases and boundary conditions
- Refactoring consistency verification
All 78 tests passing (25 + 25 + 28).
Co-authored-by: tinkle-community <tinklefund@gmail.com>

web/vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config'
+import react from '@vitejs/plugin-react'
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    globals: true,
+    environment: 'jsdom',
+    setupFiles: './src/test/setup.ts',
+    css: true,
+  },
+})