fix(share): the user picked to invite shows in the field before it is sent

The share dialog stored the pick as String(value) while its options are
keyed by numeric user ids. CustomSelect looked the pick up with a strict
comparison, found nothing and left the trigger on its placeholder, although
the Invite button was already enabled and the invite went through. The
phone opens the same dialog from the Mehr sheet, so it showed the same.

CustomSelect now compares the held value and the option values as text, so
a caller holding "5" finds the option keyed 5 and the other way round. A
held null or undefined still matches nothing. onChange keeps handing back
the option value unchanged. No other caller mixes the two kinds today; the
place form had worked around the same trap by keying its options as
strings, and its comment now says why the string stays.

Tests: CustomSelect matches across both kinds and marks the pick in the
list, the desktop dialog shows the picked name and clears after the invite,
and the phone share sheet does the same through the real dialog.

Refs #2478

client/src/components/Planner/PlaceFormModal.tsx

@@ -1196,9 +1196,8 @@ export default function PlaceFormModal(props: PlaceFormModalProps) {
                 options={[
                   { value: '', label: t('places.noCategory') },
                   ...(categories || []).map(c => ({
-                    // form.category_id is a string; CustomSelect matches options by
-                    // strict equality, so the option value must be a string too —
-                    // otherwise the chosen category never renders in the trigger.
+                    // A string like form.category_id, so the picked option hands
+                    // back the same kind of value the form already keeps.
                     value: String(c.id),
                     label: c.name,
                   })),