feat(JUVENILE-AVATARS): Foto-Avatare pro Jungtier im Wurf-Detail

- JuvenileCard-Komponente in WurfDetailPage mit 36px-Kreis-Avatar links
- Fallback auf GerbilIcon (SVG-Silhouette) wenn kein profilePhotoUrl
- URL-basiertes Fehler-Tracking (failedUrl) statt useEffect+imgError
- wuerfe.css: Flex-Layout fuer Card+Avatar, overflow:hidden/object-fit:cover
- StammbaumPage: gleiche Lint-Verletzung (react-hooks/set-state-in-effect)
  behoben (failedUrl-Pattern, kein useEffect mehr fuer Bild-Reset)
- E2E: profilePhotoUrl auf Pippa (pup-abgabe), neuer Avatar-Test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gerbil-manager-web/src/pages/wuerfe.css

@@ -0,0 +1,34 @@
+/* JUVENILE-AVATARS: photo avatar to the left of each juvenile card. */
+.gerbil-card--with-photo {
+  display: flex;
+  align-items: flex-start;
+  gap: 0.75rem;
+}
+
+.juvenile-body {
+  min-width: 0;
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  gap: 0.2rem;
+}
+
+.juvenile-photo {
+  flex: none;
+  width: 36px;
+  height: 36px;
+  border-radius: 50%;
+  overflow: hidden;
+  background: var(--color-accent-soft);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  align-self: center;
+}
+
+.juvenile-photo__avatar {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+  display: block;
+}