Update documentation for repo structure and DB practices

Added detailed sections to `AGENTS.md`:
- "Repo Snapshot (verified)" to describe the .NET 8 solution structure and current implementation state.
- "High-value Commands" with instructions for building and running the solution.
- "Architecture That Matters During Edits" to outline dependency direction, key libraries, and response contract.
- "Current Implementation Gaps (easy to miss)" to highlight incomplete implementations and areas needing verification.
- "Config/Security Gotcha" to warn about sensitive data in `appsettings.json`.

Updated `README.md`:
- Added "Wichtiger Hinweis zu DB-Spaltennamen" to explain DB column mapping practices and emphasize the need for final verification of stored procedure result sets.
- Clarified that DB field names are mapped only in the Infrastructure layer, not in Domain models.

src/infrastructure/DigitalData.TaskFlow.Infrastructure/README.md

@@ -26,6 +26,15 @@ Die Infrastructure-Schicht setzt die in Application definierten Abstraktionen ko
 - `Persistence/Models/`
   - Keyless Modelle fuer Procedure-Ergebnisse.
 
+## Wichtiger Hinweis zu DB-Spaltennamen
+
+- Spaltennamen in `Persistence/Models` (z. B. `WorkflowListingReadModel`) basieren aktuell auf:
+  - read-only Abfragen auf `sys.columns` (u. a. `TBCUST_F19_LISTING_RESULT`),
+  - beobachteten Result-Sets von `PRCUST_F19_GET_LISTING_DATA` im `table`-Modus.
+- Vor produktiven Aenderungen muss das finale SP-Resultset read-only verifiziert werden, idealerweise mit
+  `sp_describe_first_result_set` oder einer gleichwertigen Metadata-Pruefung.
+- Domain-Modelle bleiben davon getrennt: DB-Feldnamen werden nur in Infrastructure gemappt, nicht in Domain.
+
 ## Architektur-Regeln
 
 - Keine Controller- oder HTTP-Logik.