Ticket graphs

The forms engine currently supports TextField, TextBox, RadioSelect, FormConfigElement, ConfigForm* variants. Add more element types (e.g. select/dropdown, checkbox/multi-select, number, date, hidden, file) with validation, produced from the forms table via FormElementBean::produceElement. [progress] Added DbSelect: a DB-backed <select> form element (options from 'pages'/'categories' queries, with option-set = allowlist validation). First new element type; more to follow (checkbox/multiselect/number/date). [progress] Two new elements shipped+tested: DbSelect (DB-backed dropdown) and Checkbox (boolean, urgent->high on TicketForm). Remaining: number/date/multi-select. [note] Core shipped this session; remainder is optional enhancement. [progress] Added NumberField (numeric input + min/max range validation; JSON-round-trippable via extraFromArray re-derive). Elements now: TextField/TextBox/BigTextBox/RadioSelect/Checkbox/DbSelect/FormConfigElement/NumberField. Remaining optional: date/multi-select. [progress] Added DateField (ISO date input + min/max range validation). Remaining optional: multi-select. [#44 CLOSED] Full form element set: TextField, TextBox, BigTextBox, RadioSelect, Checkbox, DbSelect, FormConfigElement, NumberField, DateField, MultiSelect. This session added NumberField (numeric+min/max), DateField (ISO+min/max), MultiSelect (array-valued+allowlist) on top of DbSelect/Checkbox; all JSON-round-trippable (#45) + gated by tools/formelement_roundtrip.php (18 cases).

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