Refactor: Rename DocumentOperator to DocumentService

Updated project and solution files to rename and restructure
`DocumentOperator` to `DocumentService`. Modified project
references in `DocumentService.API.csproj`, `DocumentService.Application.csproj`,
and `DocumentService.Infrastructure.csproj` to reflect the new
naming convention. Updated `DocumentService.sln` to remove
old project references, add new ones, and adjust configuration
and nested project mappings accordingly. This change aligns
the project structure with the new naming convention.

DocumentService.Application/Common/DTOs/SwissQrCodeExtractionResult.cs

@@ -0,0 +1,37 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Response containing extracted Swiss QR Code in dual format.
+/// </summary>
+/// <param name="Bill">Parsed Swiss QR Bill (structured format)</param>
+/// <param name="RawLines">Raw Swiss QR Code lines (original newline-separated format)</param>
+/// <example>
+/// {
+///   "bill": {
+///     "version": "V2_0",
+///     "amount": 630.20,
+///     "currency": "CHF",
+///     "account": "CH953000520280564701R",
+///     "creditor": {
+///       "type": "Structured",
+///       "name": "ALMAT AG",
+///       "town": "Tagelswangen"
+///     },
+///     "referenceType": "QRR",
+///     "reference": "000000000000000000252080824"
+///   },
+///   "rawLines": [
+///     "SPC",
+///     "0200",
+///     "1",
+///     "CH953000520280564701R",
+///     "S",
+///     "ALMAT AG",
+///     "..."
+///   ]
+/// }
+/// </example>
+public record SwissQrCodeExtractionResult(
+    SwissQrBillDto Bill,
+    IReadOnlyList<string> RawLines
+);