feat(zns-importer): add ZNSImportService with tests and REST controller

- Created `ZnsImportService` to handle uploading, parsing, and persisting ZNS data from legacy `.zip` files.
- Introduced corresponding test cases in `ZnsImportServiceTest` for handling edge cases including imports and updates.
- Added REST controller `ZnsImportController` for initiating import jobs and retrieving their status.
- Defined `ZnsImportResult` data structure for reporting results of import operations.
- Established database configuration specific to ZNS importer for development profile.
- Updated utility libraries with `FixedWidthLineReader` for fixed-width string parsing.
- Refactored architecture by placing parser logic in `core:zns-parser` for reuse across backend and Compose Desktop app.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

docs/01_Architecture/MASTER_ROADMAP.md

@@ -141,10 +141,12 @@ und über definierte Schnittstellen kommunizieren.
 
 #### 🧹 Agent: Curator & Lead Architect (ZNS-Importer)
 
-*   [ ] **ZNS-Importer (MVP):** Implementierung des ZNS-Importers für Stammdaten.
+*   [x] **ZNS-Importer (MVP) – Phase 1 & 2:** `core:zns-parser` (KMP), `ZnsLegacyParsers` (alle 4 Dateitypen, CP850),
+    `ZnsImportService` (Orchestrator, ZIP in-memory, Upsert), Unit-Tests grün.
     → Detaillierte Planung: `docs/01_Architecture/Roadmap_ZNS_Importer.md`
-  *   [ ] Backend-Infrastruktur & CP850 Parser (Phase 1)
-  *   [ ] Domain-Mapping & Upsert in DB (Phase 2)
+  *   [x] Backend-Infrastruktur & CP850 Parser (Phase 1 – Parser/Modul)
+  *   [x] Domain-Mapping & Upsert in DB (Phase 2)
+  *   [ ] REST-API & Job-Management (Phase 1 – Controller/Job-Registry)
   *   [ ] Frontend-Integration mit File-Picker & Status-Polling (Phase 3)
 
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