fix: complete image pipeline - rotation, URL, preview

- Add rotation_degrees parameter to ImageProcessor.process_photo()
- Pass rotation through _auto_save_photo_from_extraction() to processor
- Allow no-crop fallback when crop_bounds is None
- Add buildPhotoUrl() helper to resolve backend URLs correctly
- Update frontend components to use backend URL for image sources
- Replace Use/Skip Photo buttons with checkbox in AI extraction UI
- Add images/ to .gitignore to prevent accidental commits

Addresses: rotation never applied, image 404s (relative to Next.js not backend), preview blank in edit form

frontend/app/inventory/page.tsx

@@ -2,7 +2,7 @@
 
 import { useState, useEffect, useCallback } from 'react';
 import { db, Item } from '@/lib/db';
-import { inventoryApi } from '@/lib/api';
+import { inventoryApi, getBackendUrl } from '@/lib/api';
 import PageShell from '@/components/PageShell';
 import Scanner from '@/components/Scanner';
 import StatCard from '@/components/StatCard';
@@ -41,6 +41,7 @@ export default function InventoryPage() {
   const [inventory, setInventory] = useState<Item[]>([]);
   const [stats, setStats] = useState<any>(null);
   const [currentUser, setCurrentUser] = useState<any | null>(null);
+  const [backendUrl, setBackendUrl] = useState<string>('');
 
   const {
     searchQuery,
@@ -85,7 +86,8 @@ export default function InventoryPage() {
     if (savedUser) {
       setCurrentUser(JSON.parse(savedUser));
     }
-    
+
+    getBackendUrl().then(setBackendUrl);
     loadData();
   }, []);
 
@@ -311,6 +313,7 @@ export default function InventoryPage() {
             }
           }}
           categoriesList={categoriesList}
+          backendUrl={backendUrl}
         />
       </div>