FEAT-12a: provider-agnostic sale-ad AI core - AiOptions (env-only), German prompt builder w/ few-shot, OpenAI-compatible chat-completions client (no SDK)

GerbilManagerWebAPI/SaleAd/SaleAdModels.cs

@@ -0,0 +1,39 @@
+namespace GerbilManagerWebAPI.SaleAd
+{
+    /// <summary>
+    /// FEAT-12a: request/response contract of POST /gerbils/sale-ad — FROZEN,
+    /// mirror of the frontend (gerbil-manager-web/src/api/saleAd.ts).
+    /// </summary>
+    public sealed record SaleAdAnimal(
+        string Name,
+        string? Farbschlag,
+        /// <summary>ISO "YYYY-MM-DD" (frontend sends the DTO string verbatim).</summary>
+        string? DateOfBirth,
+        string? Notes);
+
+    public sealed record SaleAdRequest(
+        List<SaleAdAnimal> Animals,
+        /// <summary>e.g. "FREI" / "LOCKER RESERVIERT Anna" / "RESERVIERT".</summary>
+        string StatusLine,
+        /// <summary>Free-text style hints/wishes from the user.</summary>
+        string Hints);
+
+    public sealed record SaleAdResponse(string Text);
+
+    /// <summary>
+    /// Error body for the non-200 paths. The code string "AiKeyMissing" is FROZEN —
+    /// Kevin's UI maps it to the German "API-Schlüssel noch nicht konfiguriert" hint.
+    /// </summary>
+    public sealed record SaleAdError(string Code, string Message);
+
+    public enum SaleAdStatus
+    {
+        Ok,
+        /// <summary>AI section not (fully) configured -> HTTP 503, code "AiKeyMissing".</summary>
+        NotConfigured,
+        /// <summary>Provider call failed -> HTTP 502, code "AiUpstreamError".</summary>
+        UpstreamError,
+    }
+
+    public sealed record SaleAdResult(SaleAdStatus Status, string? Text, string? Error = null);
+}