feat: add comprehensive form integration examples

- Complete Registration Form with multi-step validation
- Product Creation Form demonstrating all controlled components
- Form Validation Showcase with various validation scenarios
- Real-world usage patterns with error handling and submit states
- Comprehensive documentation for each example

Components integrated:
- ControlledInput (text, email, password, number)
- ControlledCheckbox (terms, preferences, status flags)
- ControlledSelect (country, category selection)
- ControlledDatePicker (birth date, launch date with constraints)
- ControlledCurrencyInput (pricing with validation)
- ControlledTextArea (descriptions, tags)

Validation features:
- Real-time validation with react-hook-form
- Complex business rules (age verification, price ranges)
- Format validation (email, SKU patterns, dimensions)
- Cross-field validation (password confirmation)
- Submit handling with loading states and success feedback

Author: codegen-sh[bot]