Adds comprehensive mock data repositories and seeding infrastructure

Implements polymorphic data seeding mechanism for initial application setup

- Adds Mock repositories for Event, Booking, Customer, and Resource entities
- Creates DataSeeder to automatically populate IndexedDB from JSON sources
- Enhances index.ts initialization process with data seeding step
- Adds mock JSON data files for comprehensive test data

Improves offline-first and development testing capabilities

wwwroot/data/mock-customers.json

@@ -0,0 +1,49 @@
+[
+  {
+    "id": "CUST001",
+    "name": "Sofie Nielsen",
+    "phone": "+45 23 45 67 89",
+    "email": "sofie.nielsen@email.dk"
+  },
+  {
+    "id": "CUST002",
+    "name": "Emma Andersen",
+    "phone": "+45 31 24 56 78",
+    "email": "emma.andersen@email.dk"
+  },
+  {
+    "id": "CUST003",
+    "name": "Freja Christensen",
+    "phone": "+45 42 67 89 12",
+    "email": "freja.christensen@email.dk"
+  },
+  {
+    "id": "CUST004",
+    "name": "Laura Pedersen",
+    "phone": "+45 51 98 76 54"
+  },
+  {
+    "id": "CUST005",
+    "name": "Ida Larsen",
+    "phone": "+45 29 87 65 43",
+    "email": "ida.larsen@email.dk"
+  },
+  {
+    "id": "CUST006",
+    "name": "Caroline Jensen",
+    "phone": "+45 38 76 54 32",
+    "email": "caroline.jensen@email.dk"
+  },
+  {
+    "id": "CUST007",
+    "name": "Mathilde Hansen",
+    "phone": "+45 47 65 43 21",
+    "email": "mathilde.hansen@email.dk"
+  },
+  {
+    "id": "CUST008",
+    "name": "Olivia Sørensen",
+    "phone": "+45 56 54 32 10",
+    "email": "olivia.sorensen@email.dk"
+  }
+]