Feature: Tagebuch Cover-Bild (Favorit-Funktion) für diary_media

- Migration: diary_media.is_cover (INTEGER DEFAULT 0)
- Upload: erstes Item eines Eintrags automatisch is_cover=1
- Neuer Endpoint: PATCH /diary/{id}/media/{mid}/cover
- GET-Endpoints geben is_cover + cover_url zurück
- Frontend: Stern-Button (⭐) in Gallery-Detail und Edit-Formular
- Timeline-Karte verwendet cover_url als Vorschaubild
- SW by-v212, APP_VER 186

backend/static/js/api.js

@@ -127,6 +127,9 @@ const API = (() => {
     deleteMediaItem(dogId, entryId, mediaId) {
       return del(`/dogs/${dogId}/diary/${entryId}/media/${mediaId}`);
     },
+    setCover(dogId, entryId, mediaId) {
+      return patch(`/dogs/${dogId}/diary/${entryId}/media/${mediaId}/cover`, {});
+    },
     nearby(dogId, lat, lon) {
       return get(`/dogs/${dogId}/diary/nearby?lat=${lat}&lon=${lon}`);
     },
@@ -149,6 +152,12 @@ const API = (() => {
     deleteDocument(dogId, id) {
       return del(`/dogs/${dogId}/health/${id}/dokument`);
     },
+    uploadMedia(dogId, entryId, formData) {
+      return upload(`/dogs/${dogId}/health/${entryId}/media`, formData);
+    },
+    deleteMedia(dogId, entryId, mediaId) {
+      return del(`/dogs/${dogId}/health/${entryId}/media/${mediaId}`);
+    },
     kiZusammenfassung(dogId) {
       return post(`/dogs/${dogId}/health/ki-zusammenfassung`);
     },