feat: Refactor code structure and optimize performance across multiple modules

mobile-apps/client-app/lib/features/invoice/data/invoices_gql.dart

@@ -0,0 +1,145 @@
+const String getInvoicesQuery = '''
+query GetInvoices (\$status: InvoiceStatus, \$first: Int!, \$after: String) {
+  client_invoices( status: \$status, first: \$first, after: \$after) {
+    pageInfo {
+      hasNextPage
+      hasPreviousPage
+      startCursor
+      endCursor
+      total
+      count
+      currentPage
+      lastPage
+    }
+    edges {
+      ...invoice
+      cursor
+    }
+  }
+}
+
+
+fragment invoice on InvoiceEdge {
+  node {
+    id
+    business {
+      id
+      name
+      avatar
+      registration
+      contact{
+        id
+        first_name
+        last_name
+        email
+        phone
+      }
+    }
+    event {
+      id
+      status
+      start_time
+      end_time
+      contract_type
+      ...hub
+      name
+      date
+      purchase_order
+    }
+    status
+    contract_type
+    contract_value
+    total
+    addons_amount
+    work_amount
+    issued_at
+    due_at
+    ...items
+    dispute {
+      id
+      reason
+      details
+      support_note
+    }
+  }
+}
+
+fragment items on Invoice {
+  items {
+    id
+    staff {
+      id
+      first_name
+      last_name
+      email
+      phone
+      address
+    }
+    position {
+      id
+      start_time
+      end_time
+      break
+      count
+      rate
+      ...business_skill
+      staff{
+      id
+        pivot {
+          id
+          status
+          start_at
+          end_at
+          clock_in
+          clock_out
+        }
+      }
+    }
+    work_hours
+    rate
+    addons_amount
+    work_amount
+    total_amount
+  }
+}
+
+fragment business_skill on EventShiftPosition {
+  business_skill {
+    id
+    skill {
+      id
+      name
+      slug
+    }
+    price
+    is_active
+  }
+}
+
+fragment hub on Event {
+  hub {
+    id
+    name
+    full_address {
+      formatted_address
+    }
+  }
+}
+
+''';
+
+const String approveInvoiceMutation = '''
+mutation ApproveInvoice(\$id: ID!) {
+  confirm_client_invoice(id: \$id) {
+    id
+  }
+}
+''';
+
+const String disputeInvoiceMutation = '''
+mutation DisputeInvoice(\$id: ID!, \$reason: String!, \$comment: String!) {
+  dispute_client_invoice(id: \$id, reason: \$reason, details: \$comment) {
+    id
+  }
+}
+''';