feat: implement inventory CRUD UI components (#18 #19 #20 #21)

Week 2 core inventory management:

**Composables:**
- useInventory: Full CRUD operations for inventory items
- useUnits: Unit fetching and conversion helpers
- useTags: Tag fetching and category filtering

**Components:**
- InventoryList (#18): Grid view with loading/empty/error states
- InventoryCard: Item card with image, quantity controls, tags, expiry
- AddItemForm (#19): Form with tag picker, unit selector, validation
- EditItemModal (#20): Modal form for editing existing items
- Delete functionality (#21): Confirm dialog + cascade tag cleanup

**Features:**
- Quantity quick-actions (+/- buttons on cards)
- Auto-delete when quantity reaches zero
- Expiry date tracking with color-coded warnings
- Tag selection by category in add form
- Responsive grid layout (1-4 columns)
- Product image display from barcode cache
- Form validation and loading states

Closes #18, #19, #20, #21

app/components/inventory/InventoryCard.vue

@@ -0,0 +1,151 @@
+<template>
+  <UCard class="hover:shadow-lg transition-shadow">
+    <!-- Item Image -->
+    <div class="aspect-square bg-gray-100 rounded-lg mb-3 overflow-hidden">
+      <img 
+        v-if="item.product?.image_url" 
+        :src="item.product.image_url" 
+        :alt="item.name"
+        class="w-full h-full object-cover"
+      />
+      <div v-else class="w-full h-full flex items-center justify-center">
+        <UIcon name="i-heroicons-cube" class="w-16 h-16 text-gray-300" />
+      </div>
+    </div>
+
+    <!-- Item Info -->
+    <div class="space-y-2">
+      <div>
+        <h3 class="font-semibold text-gray-900 truncate">{{ item.name }}</h3>
+        <p v-if="item.product?.brand" class="text-sm text-gray-600 truncate">
+          {{ item.product.brand }}
+        </p>
+      </div>
+
+      <!-- Quantity -->
+      <div class="flex items-center justify-between">
+        <span class="text-lg font-medium text-gray-900">
+          {{ item.quantity }} {{ item.unit?.abbreviation }}
+        </span>
+
+        <!-- Quick Actions -->
+        <div class="flex gap-1">
+          <UButton 
+            icon="i-heroicons-minus"
+            size="xs"
+            color="gray"
+            variant="ghost"
+            @click="$emit('update-quantity', item.id, -1)"
+            :disabled="item.quantity <= 1"
+          />
+          <UButton 
+            icon="i-heroicons-plus"
+            size="xs"
+            color="gray"
+            variant="ghost"
+            @click="$emit('update-quantity', item.id, 1)"
+          />
+        </div>
+      </div>
+
+      <!-- Tags -->
+      <div v-if="item.tags && item.tags.length > 0" class="flex flex-wrap gap-1">
+        <UBadge 
+          v-for="tagItem in item.tags.slice(0, 3)" 
+          :key="tagItem.tag.id"
+          :style="{ backgroundColor: tagItem.tag.color }"
+          size="xs"
+          class="text-white"
+        >
+          {{ tagItem.tag.icon }} {{ tagItem.tag.name }}
+        </UBadge>
+        <UBadge v-if="item.tags.length > 3" size="xs" color="gray">
+          +{{ item.tags.length - 3 }}
+        </UBadge>
+      </div>
+
+      <!-- Expiry Warning -->
+      <div v-if="daysUntilExpiry !== null" class="text-xs">
+        <UBadge 
+          :color="expiryColor"
+          variant="soft"
+          class="w-full justify-center"
+        >
+          <UIcon :name="expiryIcon" class="mr-1" />
+          {{ expiryText }}
+        </UBadge>
+      </div>
+    </div>
+
+    <!-- Action Buttons -->
+    <template #footer>
+      <div class="flex gap-2">
+        <UButton 
+          icon="i-heroicons-pencil"
+          size="sm"
+          color="gray"
+          variant="soft"
+          class="flex-1"
+          @click="$emit('edit', item)"
+        >
+          Edit
+        </UButton>
+        <UButton 
+          icon="i-heroicons-trash"
+          size="sm"
+          color="red"
+          variant="soft"
+          @click="$emit('delete', item.id)"
+        >
+          Delete
+        </UButton>
+      </div>
+    </template>
+  </UCard>
+</template>
+
+<script setup lang="ts">
+const props = defineProps<{
+  item: any
+}>()
+
+defineEmits<{
+  edit: [item: any]
+  delete: [id: string]
+  'update-quantity': [id: string, change: number]
+}>()
+
+// Calculate days until expiry
+const daysUntilExpiry = computed(() => {
+  if (!props.item.expiry_date) return null
+  
+  const today = new Date()
+  const expiry = new Date(props.item.expiry_date)
+  const diff = Math.ceil((expiry.getTime() - today.getTime()) / (1000 * 60 * 60 * 24))
+  
+  return diff
+})
+
+// Expiry badge styling
+const expiryColor = computed(() => {
+  if (daysUntilExpiry.value === null) return 'gray'
+  if (daysUntilExpiry.value < 0) return 'red'
+  if (daysUntilExpiry.value <= 3) return 'orange'
+  if (daysUntilExpiry.value <= 7) return 'yellow'
+  return 'green'
+})
+
+const expiryIcon = computed(() => {
+  if (daysUntilExpiry.value === null) return 'i-heroicons-calendar'
+  if (daysUntilExpiry.value < 0) return 'i-heroicons-exclamation-triangle'
+  return 'i-heroicons-clock'
+})
+
+const expiryText = computed(() => {
+  if (daysUntilExpiry.value === null) return 'No expiry'
+  if (daysUntilExpiry.value < 0) return `Expired ${Math.abs(daysUntilExpiry.value)} days ago`
+  if (daysUntilExpiry.value === 0) return 'Expires today'
+  if (daysUntilExpiry.value === 1) return 'Expires tomorrow'
+  return `Expires in ${daysUntilExpiry.value} days`
+})
+</script>