refactor(composables): migrate JS composables to TypeScript (F3.2)

Convert 7 composables from JS to TS with proper type annotations:
useApi, useCustomFields, useProfileSession, useProfiles, useToast,
useMachineTypesApi, useMachines. Remove deprecated stubs
useComponentModels.js and usePieceModels.js.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/composables/useToast.ts

@@ -0,0 +1,80 @@
+import { ref } from 'vue'
+
+export type ToastType = 'success' | 'error' | 'warning' | 'info'
+
+export interface Toast {
+  id: number
+  message: string
+  type: ToastType
+  visible: boolean
+}
+
+const toasts = ref<Toast[]>([])
+const MAX_TOASTS = 3
+let nextId = 1
+
+export function useToast() {
+  const showToast = (message: string, type: ToastType = 'info', duration = 3500): number => {
+    const id = nextId++
+    const toast: Toast = {
+      id,
+      message,
+      type,
+      visible: true,
+    }
+
+    if (toasts.value.length >= MAX_TOASTS) {
+      toasts.value.shift()
+    }
+
+    toasts.value.push(toast)
+
+    // Auto-remove after duration
+    setTimeout(() => {
+      removeToast(id)
+    }, duration)
+
+    return id
+  }
+
+  const showSuccess = (message: string, duration = 5000): number => {
+    return showToast(message, 'success', duration)
+  }
+
+  const showError = (message: string, duration = 5000): number => {
+    return showToast(message, 'error', duration)
+  }
+
+  const showWarning = (message: string, duration = 6000): number => {
+    return showToast(message, 'warning', duration)
+  }
+
+  const showInfo = (message: string, duration = 5000): number => {
+    return showToast(message, 'info', duration)
+  }
+
+  const removeToast = (id: number): void => {
+    const index = toasts.value.findIndex((toast) => toast.id === id)
+    if (index !== -1 && toasts.value[index]) {
+      toasts.value[index].visible = false
+      setTimeout(() => {
+        toasts.value.splice(index, 1)
+      }, 300) // Animation duration
+    }
+  }
+
+  const clearAll = (): void => {
+    toasts.value = []
+  }
+
+  return {
+    toasts,
+    showToast,
+    showSuccess,
+    showError,
+    showWarning,
+    showInfo,
+    removeToast,
+    clearAll,
+  }
+}