refactor : merge Inventory_frontend submodule into frontend/ directory

Merges the full git history of Inventory_frontend into the monorepo
under frontend/. Removes the submodule in favor of a unified repo.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/app/shared/utils/apiHelpers.ts

@@ -0,0 +1,16 @@
+/**
+ * Shared API response helpers.
+ *
+ * Extracted from 10+ composables/components that each had an identical local
+ * copy of extractCollection (parsing hydra:member / member / data / array).
+ */
+
+export function extractCollection<T = any>(payload: unknown): T[] {
+  if (Array.isArray(payload)) return payload as T[]
+  const p = payload as Record<string, unknown> | null
+  if (Array.isArray(p?.member)) return p!.member as T[]
+  if (Array.isArray(p?.['hydra:member'])) return p!['hydra:member'] as T[]
+  if (Array.isArray(p?.items)) return p!.items as T[]
+  if (Array.isArray(p?.data)) return p!.data as T[]
+  return []
+}