feat(ai): add AI trace tracking and admin panel

- Add AiTrace model to Prisma schema with relations to User
- Implement AiTraceService with CRUD operations for AI traces
- Add new admin panel for AI traces with filtering and detail views
- Integrate trace persistence in receipt import flow
- Add API endpoints for listing and retrieving AI traces
- Update Flutter admin UI with new AI tab and navigation
- Add new domain models for AI traces and details
- Add migration for AiTrace table creation

BREAKING CHANGE: None

backend/src/receipt-import/receipt-import.parse-flow.spec.ts

@@ -12,12 +12,13 @@ describe('ReceiptImportService parseReceipt flow', () => {
     cat(51, 'Godis', 'Glass, godis & snacks > Godis'),
   ];
 
-  const prismaMock = {
-    receiptAlias: { findMany: jest.fn() },
-    product: { findMany: jest.fn() },
-    unitMapping: { findMany: jest.fn() },
-    user: { findUnique: jest.fn() },
-  };
+  const prismaMock = {
+    aiTrace: { create: jest.fn() },
+    receiptAlias: { findMany: jest.fn() },
+    product: { findMany: jest.fn() },
+    unitMapping: { findMany: jest.fn() },
+    user: { findUnique: jest.fn() },
+  };
 
   const aiServiceMock = {
     suggestCategory: jest.fn(),
@@ -80,14 +81,21 @@ describe('ReceiptImportService parseReceipt flow', () => {
       confidence: 'low',
     });
 
-    jest
-      .spyOn(service as any, 'parseReceiptViaImporter')
-      .mockResolvedValue([
-        { rawName: 'MIXAD VARA', quantity: 1, unit: 'st' },
-        { rawName: 'GLOBAL CHOKLAD', quantity: 1, unit: 'st' },
-        { rawName: 'SPECIALPRODUKT 1st', quantity: 1, unit: 'st' },
-        { rawName: 'helt okänd vara', quantity: 1, unit: 'st' },
-      ]);
+    jest
+      .spyOn(service as any, 'parseReceiptViaImporter')
+      .mockResolvedValue({
+        items: [
+          { rawName: 'MIXAD VARA', quantity: 1, unit: 'st' },
+          { rawName: 'GLOBAL CHOKLAD', quantity: 1, unit: 'st' },
+          { rawName: 'SPECIALPRODUKT 1st', quantity: 1, unit: 'st' },
+          { rawName: 'helt okänd vara', quantity: 1, unit: 'st' },
+        ],
+        trace: {
+          prompt: 'test prompt',
+          rawOutput: '{"items":[]}',
+          normalizedOutput: { items: [] },
+        },
+      });
 
     const file = {
       buffer: Buffer.from('dummy'),