feat: add TagManager and tag filtering (#30 #31)

Issue #30 - TagManager component:
- Create/delete tags with name, category, icon, color
- Color picker with hex input
- Organized display by category
- Integrated in settings page with tabs

Issue #31 - Tag filter for inventory:
- TagFilter component with multi-select
- Filter button in inventory header
- Active filter display with removable badges
- Filters items by selected tags (OR logic)
- Clean "Clear" button

Updates:
- Extended useTags composable with createTag, deleteTag
- Enhanced settings page with tab navigation
- Improved inventory filtering UX

Closes #30, #31

app/composables/useTags.ts

@@ -37,8 +37,50 @@ export const useTags = () => {
     return { data, error: null }
   }
 
+  /**
+   * Create a new tag
+   */
+  const createTag = async (tag: {
+    name: string
+    category: string
+    icon?: string | null
+    color: string
+  }) => {
+    const { data, error } = await supabase
+      .from('tags')
+      .insert(tag)
+      .select()
+      .single()
+
+    if (error) {
+      console.error('Error creating tag:', error)
+      return { data: null, error }
+    }
+
+    return { data, error: null }
+  }
+
+  /**
+   * Delete a tag
+   */
+  const deleteTag = async (tagId: string) => {
+    const { error } = await supabase
+      .from('tags')
+      .delete()
+      .eq('id', tagId)
+
+    if (error) {
+      console.error('Error deleting tag:', error)
+      return { error }
+    }
+
+    return { error: null }
+  }
+
   return {
     getTags,
-    getTagsByCategory
+    getTagsByCategory,
+    createTag,
+    deleteTag
   }
 }