Compute defaultValue on client-side #4234

[Copilot]

Moved defaultValue computation from server-side to client-side across all input types. Each input type now implements createDefaultValue() to parse and validate default values according to its value type.

Changes by input type

• Checkbox: Parses 'checked' string to boolean
• ComboBox, NoInputTypeFoundView, TextInputType: Validates string input, returns null for non-strings
• NumberInputType (Double, Long): Validates numeric input, returns null for non-numbers
• Date, Time: Pattern-matches ISO format; falls back to RelativeTimeParser for expressions like +1d, -2h, now
• DateTimeRange, PrincipalSelector: Returns null (no default values supported)

Supporting changes

• RelativeTimeParser: Added parseToDate() and parseToTime() methods to support date/time-specific relative expressions
• DateHelper.isoValueToDate(): Added mode parameter to support date-only and time-only ISO formatting
• DateTime, Instant: Removed server-side default value injection logic

Example usage:

// Date input with relative time expression
createDefaultValue('+7d')  // Returns value 7 days from now

// Number input with validation
createDefaultValue(42)     // Returns numeric value
createDefaultValue('foo')  // Returns null value

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