feat(10-03): tabs, toggles, relation fields, form lifecycle and settings pages

- FormTabs groups fields by tab (untabbed fields in the default tab) as a
  segmented tablist; a tab holding invalid fields after a 422 shows a
  count badge and the form switches to the first invalid field
- switch, checkbox and relation join the renderer registry: toggle cards
  (role=switch, 20px checkbox) keep a numeric value numeric; relation
  fields are read-only labels from meta.labels, a searchable single
  select over fields/{field}/options with emptyOption first, or ordered
  removable chips with an appending search (300 ms debounce, 20 per
  page, more on scroll or the more action)
- FormView gets the back button, record title and update subtitle, a
  sticky footer (Usuń with deleteConfirm then DELETE, Anuluj, Zapisz i
  zamknij to the mapped redirectClose, Zapisz), and asks before leaving a
  dirty form on any route change plus a beforeunload guard
- Settings: the rail pins Ustawienia to the bottom when /settings is
  non-empty; /settings lists pages by category; /settings/:code renders
  the settings schema through FormGrid and the registry, PUTs the values
  and maps a 422 like the record form
- New backend::lang keys (form.more_options, tab_default, discard,
  settings.back); form and settings smoke tests; boardwalk/dist rebuilt

admin/tests/fixtures/widgets.form-schema.json

@@ -2,8 +2,20 @@
   "data": {
     "name": "Widget",
     "fields": [
-      { "name": "name", "label": "Name", "type": "text", "span": "left", "required": true },
-      { "name": "code", "label": "Code", "type": "text", "span": "right", "comment": "Unique widget code" },
+      {
+        "name": "name",
+        "label": "Name",
+        "type": "text",
+        "span": "left",
+        "required": true
+      },
+      {
+        "name": "code",
+        "label": "Code",
+        "type": "text",
+        "span": "right",
+        "comment": "Unique widget code"
+      },
       {
         "name": "size",
         "label": "Size",
@@ -11,28 +23,139 @@
         "span": "left",
         "emptyOption": "— none —",
         "options": [
-          { "value": "s", "label": "Small" },
-          { "value": "m", "label": "Medium" },
-          { "value": "l", "label": "Large" }
+          {
+            "value": "s",
+            "label": "Small"
+          },
+          {
+            "value": "m",
+            "label": "Medium"
+          },
+          {
+            "value": "l",
+            "label": "Large"
+          }
         ]
       },
-      { "name": "weight", "label": "Weight", "type": "number", "span": "right" },
-      { "name": "notes", "label": "Notes", "type": "textarea", "span": "full", "size": "small" },
-      { "name": "color", "label": "Colour", "type": "colorpicker", "span": "left" }
+      {
+        "name": "weight",
+        "label": "Weight",
+        "type": "number",
+        "span": "right"
+      },
+      {
+        "name": "notes",
+        "label": "Notes",
+        "type": "textarea",
+        "span": "full",
+        "size": "small"
+      },
+      {
+        "name": "color",
+        "label": "Colour",
+        "type": "colorpicker",
+        "span": "left"
+      },
+      {
+        "name": "active",
+        "label": "Active",
+        "type": "switch",
+        "span": "left",
+        "comment": "Shown in the catalogue"
+      },
+      {
+        "name": "featured",
+        "label": "Featured",
+        "type": "checkbox",
+        "span": "right",
+        "comment": "Pinned to the top"
+      },
+      {
+        "name": "maker",
+        "label": "Maker",
+        "type": "relation",
+        "span": "left",
+        "nameFrom": "name",
+        "emptyOption": "— none —"
+      },
+      {
+        "name": "tags",
+        "label": "Tags",
+        "type": "relation",
+        "span": "right",
+        "nameFrom": "name",
+        "multiple": true,
+        "required": true
+      },
+      {
+        "name": "owner",
+        "label": "Owner",
+        "type": "relation",
+        "span": "left",
+        "nameFrom": "email",
+        "emptyOption": "Current user",
+        "readOnly": true
+      },
+      {
+        "name": "serial",
+        "label": "Serial",
+        "type": "text",
+        "span": "left",
+        "tab": "Details",
+        "context": "update"
+      },
+      {
+        "name": "batch",
+        "label": "Batch",
+        "type": "text",
+        "span": "right",
+        "tab": "Details",
+        "context": [
+          "create"
+        ]
+      },
+      {
+        "name": "parts",
+        "type": "relation-manager",
+        "relation": "parts",
+        "span": "full",
+        "tab": "Parts",
+        "context": "update"
+      }
     ],
     "messages": {
-      "create": { "other": "New widget" },
-      "update": { "other": "Editing widget" },
-      "saved": { "other": "Widget „:name” saved" },
-      "deleteConfirm": { "other": "Delete this widget?" },
-      "deleted": { "other": "Widget deleted" }
+      "create": {
+        "other": "New widget"
+      },
+      "update": {
+        "other": "Editing widget"
+      },
+      "saved": {
+        "other": "Widget „:name” saved"
+      },
+      "deleteConfirm": {
+        "other": "Delete this widget?"
+      },
+      "deleted": {
+        "other": "Widget deleted"
+      }
+    },
+    "meta": {
+      "locale": "en"
     },
-    "meta": { "locale": "en" },
     "redirects": {
-      "create": { "redirect": "acme/demo/widgets/update/:id", "redirectClose": "acme/demo/widgets" },
-      "update": { "redirect": "acme/demo/widgets", "redirectClose": "acme/demo/widgets" },
+      "create": {
+        "redirect": "acme/demo/widgets/update/:id",
+        "redirectClose": "acme/demo/widgets"
+      },
+      "update": {
+        "redirect": "acme/demo/widgets",
+        "redirectClose": "acme/demo/widgets"
+      },
       "default": "acme/demo/widgets"
     }
   },
-  "meta": { "locale": "en" }
+  "meta": {
+    "locale": "en"
+  }
 }