feat(ui): drop @nstart/ui dependency (Stage 3.9)

Все font cascade bugs из последних MR были вызваны @nstart/ui pollution
(Tektur inheritance от Card parent'ов, Onest font в Button, font-primary
class overrides). Решили обрезать раньше plan'а.

What changed:

New primitives (8 файлов в src/ui/components/):
  - panel.tsx           — container с border/surface
  - field.tsx           — FieldLabel/Hint/Error typography helpers
  - text-input.tsx      — Input + label/hint/error composite
  - table.tsx           — Table/TableHeader/Body/Row/HeaderCell/Cell/Empty
  - date-picker.tsx     — native <input type=date> wrapper с label/hint/error
  - multi-select.tsx    — Radix Popover + inline checkboxes
  - single-select.tsx   — native <select> с label/hint/error chrome
  - language-switch.tsx — segmented control в Tektur uppercase

Compatibility shims (existing components extended):
  - checkbox.tsx        — + label/description/error/onChange (nstart-compat
                          synthetic event), wrap в <label> когда есть chrome
  - modal.tsx           — + panelClassName / bodyClassName props
  - form-actions.tsx    — + align prop (start/end/between)
  - tabs-simple.tsx     — TabItem.count alias for .trailing (nstart-compat)
  - table TableHead     — alias TableHeaderCell с align prop

Barrel rewrite (src/ui/index.ts):
  - Удалён 'export * from @nstart/ui'
  - Explicit exports для всех 45+ нужных символов
  - SelectOption / MultiSelectOption / LanguageOption теперь {id, label}
    с optional 'value' alias — nstart-compat без массового codemod call-sites

styles.css cleanup:
  - Removed @import @nstart/ui/styles/{fonts,theme}.css
  - Removed @source nstart/dist directive (Tailwind v4 scan)
  - Removed --text-sm: 13px override (был костыль для @nstart/ui dist)
  - Legacy color tokens (--color-carbon/ultramarain/orbit/regolith/asteroid)
    sсодержали fallback mappings — оставлены, но callsites больше не используют

Codemod: 9 файлов конвертированы legacy colors → handoff tokens
  carbon → ink, ultramarain → accent, orbit → warn, regolith → line, asteroid → mute

main.tsx:
  - NStartUiProvider → TooltipProvider (Radix)
  - DatePickerProvider убран (наш DatePicker native, no provider needed)

routes/dictionaries.$name.tsx:
  - Removed useRef-based <input>.indeterminate hack
  - Radix Checkbox принимает checked='indeterminate' declaratively

package.json: -@nstart/ui (was 0.1.3)

Bundle impact:
  before: vendor-nstart-ui chunk = 1228 KB
  after:  no nstart chunk, всё в vendor-misc (+~70 KB Radix wrappers)
  net savings: ~1.15 MB minified, ~440 KB gzip

Tests: 116 pass (1 fixed: tab role from 'button' → 'tab', Radix semantically correct).
TS strict: clean.
Browser-verified (preview): 7 utilities computed correctly, nstart bundle absent.

ordinis-admin-ui/src/ui/components/language-switch.tsx

@@ -0,0 +1,70 @@
+import { cn } from '@/lib/utils'
+
+/**
+ * LanguageSwitch — segmented control для смены i18next language.
+ * Замена @nstart/ui LanguageSwitch (тот же value/options/onChange API).
+ *
+ * <p>Compact: 3-letter codes (RU/EN/ZH...) в Tektur uppercase. Tab-like
+ * underline indicator под active. На narrow screens сворачивается в icon
+ * только (TODO mobile responsive).
+ */
+
+/** nstart-compat: {id, label}. `value` accepted as alias. */
+export type LanguageOption = {
+  id: string
+  label: string
+  /** Alias of `id`. */
+  value?: string
+  /** Short 2-3 char code (RU/EN/ZH). Default — id.toUpperCase(). */
+  short?: string
+}
+
+export type LanguageSwitchProps = {
+  value: string
+  options: LanguageOption[]
+  onChange: (id: string) => void
+  className?: string
+  'aria-label'?: string
+}
+
+export function LanguageSwitch({
+  value,
+  options,
+  onChange,
+  className,
+  'aria-label': ariaLabel,
+}: LanguageSwitchProps) {
+  return (
+    <div
+      role="radiogroup"
+      aria-label={ariaLabel ?? 'Language'}
+      className={cn(
+        'inline-flex items-center rounded-md border border-line bg-surface p-0.5 gap-0.5',
+        className,
+      )}
+    >
+      {options.map((opt) => {
+        const v = opt.id ?? opt.value!
+        const active = v === value
+        return (
+          <button
+            key={v}
+            type="button"
+            role="radio"
+            aria-checked={active}
+            onClick={() => onChange(v)}
+            title={opt.label}
+            className={cn(
+              'px-2 py-1 rounded-sm text-cap leading-none transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring',
+              active
+                ? 'bg-accent-bg text-accent'
+                : 'text-mute hover:text-ink hover:bg-surface-2',
+            )}
+          >
+            {opt.short ?? v.toUpperCase()}
+          </button>
+        )
+      })}
+    </div>
+  )
+}