style(recipes): unify custom multiplier pill with preset pills

Make the custom-multiplier pill behave and look like a single input zone:

- Wrapper is now a <label> so clicking anywhere focuses the input.
- Replace the explicit \"x\" submit button with a passive <span> suffix and
  add a visually-hidden first-tree-order submit so no-JS Enter still
  submits with the typed value (rather than the first preset pill's value).
- Wrapper cursor: text end-to-end, no pointer flicker.
- Hover/focus selector now matches the wrapper alongside the preset
  buttons, and an isCustomMultiplier flag highlights the pill in primary
  whenever a non-preset value is active (e.g. ?multiplier=12).
- Input uses field-sizing: content (with min/max) so the pill collapses
  to fit the placeholder.
- align-items: center (was baseline) so the input doesn't sit high in
  its pill.
- Tighten the multipliers row (gap 0.5rem -> 0.3rem, button min-width
  2em -> 1.8em, matching paddings) so all six pills fit on one line in
  the ingredients column.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.57.2",
+	"version": "1.57.3",
 	"private": true,
 	"type": "module",
 	"scripts": {