fix: repair recognition — migrate vision model and fix XFile handling

- Replace decommissioned llama-3.2-11b-vision-preview with
  meta-llama/llama-4-scout-17b-16e-instruct (Groq deprecation)
- Use XFile.readAsBytes() instead of File(path).readAsBytes() so
  Android content URIs (from gallery picks) are read correctly
- Add maxWidth/maxHeight constraints to image picker calls to reduce
  payload size
- Increase receiveTimeout from 30s to 120s to accommodate slow vision AI
- Log recognition errors via debugPrint instead of swallowing them

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

client/lib/features/scan/recognition_service.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
-import 'dart:io';
+
+import 'package:image_picker/image_picker.dart';
 
 import '../../core/api/api_client.dart';
 
@@ -108,7 +109,7 @@ class RecognitionService {
   final ApiClient _client;
 
   /// Recognizes food items from a receipt photo.
-  Future<ReceiptResult> recognizeReceipt(File image) async {
+  Future<ReceiptResult> recognizeReceipt(XFile image) async {
     final payload = await _buildImagePayload(image);
     final data = await _client.post('/ai/recognize-receipt', data: payload);
     return ReceiptResult(
@@ -122,7 +123,7 @@ class RecognitionService {
   }
 
   /// Recognizes food items from 1–3 product photos.
-  Future<List<RecognizedItem>> recognizeProducts(List<File> images) async {
+  Future<List<RecognizedItem>> recognizeProducts(List<XFile> images) async {
     final imageList = await Future.wait(images.map(_buildImagePayload));
     final data = await _client.post(
       '/ai/recognize-products',
@@ -134,17 +135,18 @@ class RecognitionService {
   }
 
   /// Recognizes a dish and estimates its nutritional content.
-  Future<DishResult> recognizeDish(File image) async {
+  Future<DishResult> recognizeDish(XFile image) async {
     final payload = await _buildImagePayload(image);
     final data = await _client.post('/ai/recognize-dish', data: payload);
     return DishResult.fromJson(data);
   }
 
-  Future<Map<String, String>> _buildImagePayload(File image) async {
+  Future<Map<String, String>> _buildImagePayload(XFile image) async {
     final bytes = await image.readAsBytes();
     final base64Data = base64Encode(bytes);
-    final ext = image.path.split('.').last.toLowerCase();
-    final mimeType = ext == 'png' ? 'image/png' : 'image/jpeg';
+    // XFile.mimeType may be null on some platforms; fall back to path extension.
+    final mimeType = image.mimeType ??
+        (image.path.toLowerCase().endsWith('.png') ? 'image/png' : 'image/jpeg');
     return {'image_base64': base64Data, 'mime_type': mimeType};
   }
 }

client/lib/features/scan/scan_screen.dart

@@ -1,5 +1,4 @@
-import 'dart:io';
-
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
@@ -70,19 +69,28 @@ class ScanScreen extends ConsumerWidget {
   ) async {
     final picker = ImagePicker();
 
-    List<File> files = [];
+    List<XFile> files = [];
 
     if (mode == _Mode.products) {
       // Allow up to 3 images.
-      final picked = await picker.pickMultiImage(imageQuality: 70);
+      final picked = await picker.pickMultiImage(
+        imageQuality: 70,
+        maxWidth: 1024,
+        maxHeight: 1024,
+      );
       if (picked.isEmpty) return;
-      files = picked.take(3).map((x) => File(x.path)).toList();
+      files = picked.take(3).toList();
     } else {
       final source = await _chooseSource(context);
       if (source == null) return;
-      final picked = await picker.pickImage(source: source, imageQuality: 70);
+      final picked = await picker.pickImage(
+        source: source,
+        imageQuality: 70,
+        maxWidth: 1024,
+        maxHeight: 1024,
+      );
       if (picked == null) return;
-      files = [File(picked.path)];
+      files = [picked];
     }
 
     if (!context.mounted) return;
@@ -116,7 +124,8 @@ class ScanScreen extends ConsumerWidget {
             context.push('/scan/dish', extra: dish);
           }
       }
-    } catch (e) {
+    } catch (e, s) {
+      debugPrint('Recognition error: $e\n$s');
       if (context.mounted) {
         Navigator.pop(context); // close loading
         ScaffoldMessenger.of(context).showSnackBar(