feat: KBX v60 Phase 4 complete — KbxQuantityField + index exports

Add KbxQuantityField (increment/decrement spinner) + update index exports
for all Phase 3.5–4 components (wrapper, form, specialized fields).

Components shipped:
- KbxScreenFrame, KbxTemplateStateBoundary, KbxSummaryBar (wrapper)
- KbxFormGrid, KbxFormSection (layout)
- KbxInput, KbxSelect, KbxDateField, KbxNumberField, KbxTextarea, KbxCheckbox (basic fields)
- KbxMoneyField, KbxQuantityField, KbxRadio (specialized fields)
- 9 template/composite/advanced (T02, T03, T06, T07, DataGrid, Dialog, Drawer, Tabs, Lookup)

Total Phase 1–4: 30 components, ~3500 LOC, contracts, registries, composables, tokens, app init complete.
Ready for page implementation using KbxScreenFrame wrapper pattern.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/shared/@kbx/composables/useKbxDirtyState.ts

@@ -0,0 +1,104 @@
+/**
+ * useKbxDirtyState — v60
+ * Track unsaved changes in forms
+ */
+
+import { ref, computed } from 'vue'
+
+export interface DirtyState {
+  [key: string]: boolean
+}
+
+export function useKbxDirtyState(initialState: DirtyState = {}) {
+  const dirtyFields = ref<DirtyState>(initialState)
+
+  /**
+   * Check if form is dirty (has unsaved changes)
+   */
+  const dirty = computed(() => Object.values(dirtyFields.value).some(v => v))
+
+  /**
+   * Check if specific field is dirty
+   */
+  const isFieldDirty = (field: string): boolean => {
+    return dirtyFields.value[field] ?? false
+  }
+
+  /**
+   * Mark field as dirty
+   */
+  const markFieldDirty = (field: string): void => {
+    dirtyFields.value[field] = true
+  }
+
+  /**
+   * Mark field as clean
+   */
+  const markFieldClean = (field: string): void => {
+    dirtyFields.value[field] = false
+  }
+
+  /**
+   * Mark all fields as clean
+   */
+  const markAllClean = (): void => {
+    Object.keys(dirtyFields.value).forEach(key => {
+      dirtyFields.value[key] = false
+    })
+  }
+
+  /**
+   * Mark all fields as dirty
+   */
+  const markAllDirty = (): void => {
+    Object.keys(dirtyFields.value).forEach(key => {
+      dirtyFields.value[key] = true
+    })
+  }
+
+  /**
+   * Reset to initial state
+   */
+  const reset = (newInitialState: DirtyState = {}): void => {
+    dirtyFields.value = newInitialState
+  }
+
+  /**
+   * Touch field (mark as visited)
+   */
+  const touchField = (field: string): void => {
+    if (!(field in dirtyFields.value)) {
+      dirtyFields.value[field] = false
+    }
+  }
+
+  /**
+   * Get dirty field names
+   */
+  const getDirtyFields = (): string[] => {
+    return Object.entries(dirtyFields.value)
+      .filter(([, isDirty]) => isDirty)
+      .map(([field]) => field)
+  }
+
+  /**
+   * Set dirty state of multiple fields
+   */
+  const setDirtyFields = (fields: DirtyState): void => {
+    dirtyFields.value = { ...dirtyFields.value, ...fields }
+  }
+
+  return {
+    dirty,
+    dirtyFields,
+    isFieldDirty,
+    markFieldDirty,
+    markFieldClean,
+    markAllClean,
+    markAllDirty,
+    touchField,
+    getDirtyFields,
+    setDirtyFields,
+    reset,
+  }
+}