feat(stores): add Pinia domain stores and update docs

Implement concrete Pinia stores for app UI and domain data instead of
placeholder re-exports, including seeded student records and snackbar state.

Refresh README guidance for components, plugins, and services to document the
current project structure, data flow, and usage conventions.feat(stores): add Pinia domain stores and update docs

Implement concrete Pinia stores for app UI and domain data instead of
placeholder re-exports, including seeded student records and snackbar state.

Refresh README guidance for components, plugins, and services to document the
current project structure, data flow, and usage conventions.

src/stores/breadcrumbs.ts

@@ -1 +1,124 @@
-export * from './stores/breadcrumbs'
+import type { LayoutMenuItem } from './menu'
+import { mdiHome } from '@mdi/js'
+import { defineStore } from 'pinia'
+import { computed, ref } from 'vue'
+
+export interface BreadcrumbItem {
+  title: string
+  to?: string
+  disabled?: boolean
+  icon?: string
+}
+
+interface BreadcrumbPayload {
+  path: string
+  menuItems: LayoutMenuItem[]
+  favoriteItems?: LayoutMenuItem[]
+  fallbackTitle?: string | null
+  homeLabel?: string
+  homeIcon?: string
+}
+
+function buildTrail(items: LayoutMenuItem[], targetPath: string): LayoutMenuItem[] | null {
+  const walk = (nodes: LayoutMenuItem[], trail: LayoutMenuItem[]): LayoutMenuItem[] | null => {
+    for (const node of nodes) {
+      const nextTrail = [...trail, node]
+      if (node.path && node.path === targetPath) return nextTrail
+      if (node.subItems?.length) {
+        const found = walk(node.subItems, nextTrail)
+        if (found) return found
+      }
+    }
+    return null
+  }
+
+  return walk(items || [], [])
+}
+
+function toBreadcrumbItems(
+  trail: LayoutMenuItem[],
+  homeLabel: string,
+  homeIcon: string
+): BreadcrumbItem[] {
+  const isHomePath = (path?: string) => path === '/' || path === ''
+  const startsWithHome = trail.length > 0 && isHomePath(trail[0]?.path)
+  const crumbs: BreadcrumbItem[] = []
+
+  if (!startsWithHome) {
+    crumbs.push({
+      title: homeLabel,
+      to: '/',
+      icon: homeIcon,
+    })
+  }
+
+  for (const [index, node] of trail.entries()) {
+    const isLast = index === trail.length - 1
+    crumbs.push({
+      title: node.title,
+      to: isLast ? undefined : node.path,
+      icon: startsWithHome && index === 0 ? homeIcon : undefined,
+    })
+  }
+
+  return crumbs
+}
+
+export const useBreadcrumbStore = defineStore('breadcrumbs', () => {
+  const items = ref<BreadcrumbItem[]>([])
+  const homeLabel = ref('首頁')
+  const homeIcon = ref(mdiHome)
+
+  const setBreadcrumbs = (payload: BreadcrumbPayload) => {
+    if (!payload?.path) return
+
+    homeLabel.value = payload.homeLabel ?? homeLabel.value
+    homeIcon.value = payload.homeIcon ?? homeIcon.value
+
+    const trailFromMenu = buildTrail(payload.menuItems || [], payload.path)
+    const trailFromFavorite = payload.favoriteItems?.length
+      ? buildTrail(payload.favoriteItems, payload.path)
+      : null
+    const trail = trailFromMenu || trailFromFavorite
+
+    if (trail?.length) {
+      items.value = toBreadcrumbItems(trail, homeLabel.value, homeIcon.value)
+      return
+    }
+
+    if (payload.fallbackTitle && payload.fallbackTitle !== homeLabel.value) {
+      items.value = [
+        {
+          title: homeLabel.value,
+          to: '/',
+          icon: homeIcon.value,
+        },
+        {
+          title: payload.fallbackTitle,
+        },
+      ]
+      return
+    }
+
+    items.value = [
+      {
+        title: homeLabel.value,
+        to: '/',
+        icon: homeIcon.value,
+      },
+    ]
+  }
+
+  const reset = () => {
+    items.value = []
+  }
+
+  const breadcrumbItems = computed(() => items.value)
+
+  return {
+    items,
+    breadcrumbItems,
+    setBreadcrumbs,
+    reset,
+  }
+})