feat: implement Iteration 3 — product/receipt/dish recognition

Backend:
- gemini/client.go: refactor to shared callGroq transport; add
  generateVisionContent using llama-3.2-11b-vision-preview model
- gemini/recognition.go: RecognizeReceipt, RecognizeProducts,
  RecognizeDish (vision), ClassifyIngredient (text); shared parseJSON helper
- ingredient/repository.go: add FuzzyMatch (wraps Search, returns best hit)
- recognition/handler.go: POST /ai/recognize-receipt, /ai/recognize-products,
  /ai/recognize-dish; enrichItems with fuzzy match + AI classify fallback;
  parallel multi-image processing with deduplication
- server.go + main.go: wire recognition handler under /ai routes

Flutter:
- pubspec.yaml: add image_picker ^1.1.0
- AndroidManifest.xml: add CAMERA and READ_EXTERNAL_STORAGE permissions
- Info.plist: add NSCameraUsageDescription and NSPhotoLibraryUsageDescription
- recognition_service.dart: RecognitionService wrapping /ai/* endpoints;
  RecognizedItem, ReceiptResult, DishResult models
- scan_screen.dart: mode selector (receipt / products / dish / manual);
  image source picker; loading overlay; navigates to confirm or dish screen
- recognition_confirm_screen.dart: editable list of recognized items;
  inline qty/unit editing; swipe-to-delete; batch-add to pantry
- dish_result_screen.dart: dish name, KBZHU breakdown, similar dishes chips
- app_router.dart: /scan, /scan/confirm, /scan/dish routes (no bottom nav)
- products_screen.dart: FAB now shows bottom sheet with Manual / Scan options

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

client/pubspec.lock

@@ -169,6 +169,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.1.2"
+  cross_file:
+    dependency: transitive
+    description:
+      name: cross_file
+      sha256: "28bb3ae56f117b5aec029d702a90f57d285cd975c3c5c281eaca38dbc47c5937"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.3.5+2"
   crypto:
     dependency: transitive
     description:
@@ -233,6 +241,38 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "7.0.1"
+  file_selector_linux:
+    dependency: transitive
+    description:
+      name: file_selector_linux
+      sha256: "2567f398e06ac72dcf2e98a0c95df2a9edd03c2c2e0cacd4780f20cdf56263a0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.4"
+  file_selector_macos:
+    dependency: transitive
+    description:
+      name: file_selector_macos
+      sha256: "5e0bbe9c312416f1787a68259ea1505b52f258c587f12920422671807c4d618a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.5"
+  file_selector_platform_interface:
+    dependency: transitive
+    description:
+      name: file_selector_platform_interface
+      sha256: "35e0bd61ebcdb91a3505813b055b09b79dfdc7d0aee9c09a7ba59ae4bb13dc85"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.7.0"
+  file_selector_windows:
+    dependency: transitive
+    description:
+      name: file_selector_windows
+      sha256: "62197474ae75893a62df75939c777763d39c2bc5f73ce5b88497208bc269abfd"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.3+5"
   firebase_auth:
     dependency: "direct main"
     description:
@@ -310,6 +350,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "5.0.0"
+  flutter_plugin_android_lifecycle:
+    dependency: transitive
+    description:
+      name: flutter_plugin_android_lifecycle
+      sha256: ee8068e0e1cd16c4a82714119918efdeed33b3ba7772c54b5d094ab53f9b7fd1
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.33"
   flutter_riverpod:
     dependency: "direct main"
     description:
@@ -472,6 +520,70 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.1.2"
+  image_picker:
+    dependency: "direct main"
+    description:
+      name: image_picker
+      sha256: "784210112be18ea55f69d7076e2c656a4e24949fa9e76429fe53af0c0f4fa320"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.1"
+  image_picker_android:
+    dependency: transitive
+    description:
+      name: image_picker_android
+      sha256: eda9b91b7e266d9041084a42d605a74937d996b87083395c5e47835916a86156
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.8.13+14"
+  image_picker_for_web:
+    dependency: transitive
+    description:
+      name: image_picker_for_web
+      sha256: "66257a3191ab360d23a55c8241c91a6e329d31e94efa7be9cf7a212e65850214"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.1"
+  image_picker_ios:
+    dependency: transitive
+    description:
+      name: image_picker_ios
+      sha256: "956c16a42c0c708f914021666ffcd8265dde36e673c9fa68c81f7d085d9774ad"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.8.13+3"
+  image_picker_linux:
+    dependency: transitive
+    description:
+      name: image_picker_linux
+      sha256: "1f81c5f2046b9ab724f85523e4af65be1d47b038160a8c8deed909762c308ed4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2"
+  image_picker_macos:
+    dependency: transitive
+    description:
+      name: image_picker_macos
+      sha256: "86f0f15a309de7e1a552c12df9ce5b59fe927e71385329355aec4776c6a8ec91"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2+1"
+  image_picker_platform_interface:
+    dependency: transitive
+    description:
+      name: image_picker_platform_interface
+      sha256: "567e056716333a1647c64bb6bd873cff7622233a5c3f694be28a583d4715690c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.11.1"
+  image_picker_windows:
+    dependency: transitive
+    description:
+      name: image_picker_windows
+      sha256: d248c86554a72b5495a31c56f060cf73a41c7ff541689327b1a7dbccc33adfae
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2"
   io:
     dependency: transitive
     description: