chore(docs): add CHANGELOG and operations runbook for masterdata service

- Introduced `CHANGELOG.md` to document essential changes in the Masterdata-SCS, including ADRs, database schema updates, domain logic additions, API enhancements, and observability improvements.
- Added `masterdata-ops.md` runbook detailing operational procedures such as backup, restore, import management, and troubleshooting.
- Updated roadmaps to reference the new documentation and mark relevant tasks as complete.

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

backend/services/masterdata/docs/ROADMAP.md

@@ -23,7 +23,7 @@
   aktivieren.
 - Deliverables:
   - [x] ADR-Set im Repo (Rules, DB, Import, API) → ADR-0017, ADR-0018, ADR-0019
-  - Operative Runbooks (Backup/Restore, Re-Import, Rollback)
+  - [x] Operative Runbooks (Backup/Restore, Re-Import, Rollback) -> `masterdata-ops.md`
 
 ### 2) Datenmodell & Persistenz (WK 2–4)
 
@@ -137,4 +137,4 @@
 4. [ ] ZNS‑Importer an Repositories anbinden, Idempotenz-Checks ergänzen, Mini‑ZNS Testlauf (👷🧐) *
 5. [x] API v1 Endpunkte + OpenAPI, Contract‑Tests (👷🧐)
 6. [x] Observability-Grundlagen (Metriken + Dashboards) (🐧)
-7. Curator: Docs aktualisieren, Runbooks und Changelogs pflegen (🧹)
+7. [x] Curator: Docs aktualisieren, Runbooks und Changelogs pflegen (🧹)