Media-Previews: _preview.jpg bei Upload, alle Listenansichten — SW by-v437, APP_VER 416

- media_utils: generate_preview() (Pillow, max 800px, JPEG q72) + preview_url_from()
- diary.py: Preview beim Bild-Upload, preview_url in media_items + cover_preview_url
  in Kalender-, Karten- und Listenabfragen
- forum.py: Preview in _save_upload(), foto_preview_url in Thread-Listen
- Frontend diary.js: cover_preview_url in Listenansicht, Mediengalerie, Kalender,
  Karten-Marker + Popup; onerror-Fallback auf Original
- Frontend forum.js: foto_preview_url in Thread-Karten-Thumbnails
- Admin: 'Previews generieren (Bestand)' Button → POST /admin/media/generate-previews

backend/routes/diary.py

@@ -9,7 +9,7 @@ from auth import get_current_user, require_admin
 import ki as KI
 import httpx
 import weather as weather_mod
-from media_utils import convert_media, extract_video_thumb, safe_media_path, validate_upload, extract_gps_from_exif
+from media_utils import convert_media, extract_video_thumb, safe_media_path, validate_upload, extract_gps_from_exif, generate_preview, preview_url_from
 from timeutils import safe_client_time
 
 logger = logging.getLogger(__name__)
@@ -127,8 +127,10 @@ def _fetch_media_items(conn, entry_ids: list[int]) -> dict:
     ).fetchall()
     result = {}
     for r in rows:
+        url = r["url"]
         result.setdefault(r["diary_id"], []).append({
-            "id": r["id"], "url": r["url"],
+            "id": r["id"], "url": url,
+            "preview_url": preview_url_from(url),
             "media_type": r["media_type"], "sort_order": r["sort_order"],
             "is_cover": r["is_cover"],
         })
@@ -143,7 +145,8 @@ def _entry_dict(row, dog_ids_map: dict, media_map: dict = None) -> dict:
     e["media_items"] = items
     # cover_url: Item mit is_cover=1, Fallback auf erstes Item
     cover = next((m for m in items if m.get("is_cover")), items[0] if items else None)
-    e["cover_url"]   = cover["url"] if cover else None
+    e["cover_url"]         = cover["url"] if cover else None
+    e["cover_preview_url"] = preview_url_from(e["cover_url"])
     return e
 
 
@@ -185,7 +188,12 @@ async def diary_calendar(dog_id: int, user=Depends(get_current_user)):
                ORDER BY d.datum DESC""",
             (dog_id, dog_id)
         ).fetchall()
-    return [dict(r) for r in rows]
+    result = []
+    for r in rows:
+        d = dict(r)
+        d["cover_preview_url"] = preview_url_from(d.get("cover_url"))
+        result.append(d)
+    return result
 
 
 @router.get("/{dog_id}/diary/locations")
@@ -207,7 +215,12 @@ async def diary_locations(dog_id: int, user=Depends(get_current_user)):
                ORDER BY d.datum DESC""",
             (dog_id, dog_id)
         ).fetchall()
-    return [dict(r) for r in rows]
+    result = []
+    for r in rows:
+        d = dict(r)
+        d["cover_preview_url"] = preview_url_from(d.get("cover_url"))
+        result.append(d)
+    return result
 
 
 @router.get("/{dog_id}/diary")
@@ -670,6 +683,12 @@ async def upload_media(dog_id: int, entry_id: int,
 
     if media_type == "video":
         extract_video_thumb(path)
+    elif media_type == "image":
+        preview_bytes = generate_preview(raw_data, ext)
+        if preview_bytes:
+            preview_path = os.path.splitext(path)[0] + "_preview.jpg"
+            with open(preview_path, "wb") as f:
+                f.write(preview_bytes)
 
     media_url = f"/media/diary/{filename}"