FEAT-14a: Charakterbogen on Gerbil (traits + note) + sale-ad request extension

- Gerbil.CharacterTraits (List<string>, JSON text column, opaque labels) + CharacterNote
  (string?). On GerbilDto + Input; round-trips on GET/POST/PUT. Additive migration.
- SaleAdAnimal gains Traits (German labels) + CharacterNote; prompt builder emits
  "Charakter: …" + "Charakter-Notiz: …" lines for the AI Verkaufstext.
- Tests: traits/note round-trip (POST->GET via SQLite host), empty-default, prompt inclusion.

GerbilManager.Tests/GerbilCharacterTests.cs

@@ -0,0 +1,75 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.RegularExpressions;
+using GerbilManagerWebAPI.SaleAd;
+
+namespace GerbilManager.Tests;
+
+/// <summary>FEAT-14a: Charakterbogen (traits + note) persists/round-trips, and the
+/// sale-ad prompt includes the character info.</summary>
+public class GerbilCharacterTests : IClassFixture<ApiFactory>
+{
+    private readonly HttpClient _client;
+
+    public GerbilCharacterTests(ApiFactory factory) => _client = factory.CreateClient();
+
+    [Fact]
+    public async Task CharacterTraits_and_note_round_trip()
+    {
+        var create = await _client.PostAsync("/gerbils", JsonContent.Create(new
+        {
+            name = "Charakter Test",
+            gender = "female",
+            characterTraits = new[] { "zutraulich", "handzahm" },
+            characterNote = "sehr aktiv und neugierig",
+        }));
+        Assert.Equal(HttpStatusCode.Created, create.StatusCode);
+
+        var created = await create.Content.ReadAsStringAsync();
+        // POST response is the created GerbilDto — traits serialise straight back
+        Assert.Contains("zutraulich", created);
+        Assert.Contains("handzahm", created);
+        Assert.Contains("sehr aktiv und neugierig", created);
+
+        var id = Regex.Match(created, "\"id\":\"([^\"]+)\"").Groups[1].Value;
+        Assert.NotEqual("", id);
+
+        // re-read from the DB to prove persistence (not just echo)
+        var fetched = await _client.GetStringAsync($"/gerbils/{id}");
+        Assert.Contains("zutraulich", fetched);
+        Assert.Contains("handzahm", fetched);
+        Assert.Contains("sehr aktiv und neugierig", fetched);
+    }
+
+    [Fact]
+    public async Task Omitting_traits_defaults_to_empty_list()
+    {
+        var create = await _client.PostAsync("/gerbils", JsonContent.Create(new
+        {
+            name = "Ohne Charakter",
+            gender = "male",
+        }));
+        Assert.Equal(HttpStatusCode.Created, create.StatusCode);
+        var body = await create.Content.ReadAsStringAsync();
+        Assert.Contains("\"characterTraits\":[]", body.Replace(" ", ""));
+    }
+
+    [Fact]
+    public void SaleAd_prompt_includes_traits_and_note()
+    {
+        var request = new SaleAdRequest(
+            Animals: new List<SaleAdAnimal>
+            {
+                new("Bella", "Agouti", "2025-01-15", "verspielt",
+                    Traits: new List<string> { "zutraulich", "handzahm" },
+                    CharacterNote: "liebt Sonnenblumenkerne"),
+            },
+            StatusLine: "FREI",
+            Hints: "");
+
+        var prompt = SaleAdPromptBuilder.BuildUserPrompt(request);
+
+        Assert.Contains("Charakter: zutraulich, handzahm", prompt);
+        Assert.Contains("liebt Sonnenblumenkerne", prompt);
+    }
+}