Perf: 9 Performance-Fixes — SW by-v1072

Backend:
- DB: 3 neue Indizes (forum_posts thread+user, routes user) — Forum/Routen-Queries
- Caching: cache.py (TTL-Cache ohne neue Dependency) für 5 statische Listen
  (training_exercises, pflege_tipps, wiki_stats, wiki_gruppen, help_articles)
- diary.py + breeder_photos.py: Bildverarbeitung (ffmpeg/PIL/EXIF) per
  run_in_executor → blockiert Event-Loop nicht mehr
- scheduler.py: 11 kollidierende Jobs auf 5-Min-Intervalle gestaggert, coalesce=True
- social.py: ORDER BY RANDOM() ohne LIMIT in 2 Stellen gefixt
- alerts.py: Haversine-Loop bekommt SQL-Bounding-Box-Vorfilter

Frontend:
- sw.js: Tile-Cache mit LRU-Eviction (max 500 Einträge)
- admin.js: Event-Listener-Leak — Tab-Klicks per Delegation statt N Listener
- api.js: compressImage() Helper — Client-seitiges Resize auf max 2000px
  (HEIC/Videos/<500KB unverändert), integriert in 8 Upload-Stellen
  (diary, dog-profile×2, walks, poison, lost, health×2)

Bump APP_VER 1071 → 1072 (sw.js, app.js, main.py, index.html)

backend/routes/dogs.py

@@ -9,6 +9,20 @@ from database import db
 from auth import get_current_user, has_pro_access
 from routes.push import send_push_to_user
 from media_utils import safe_media_path, preview_url_from
+from cache import ttl_cache
+
+
+# ------------------------------------------------------------------
+# Pflege-Tipps sind statische Stamm-Daten → 1h TTL-Cache
+# (Filterung pro Hund passiert weiter unten in-memory, NICHT gecached)
+# ------------------------------------------------------------------
+@ttl_cache(ttl=3600)
+def _load_all_pflege_tipps() -> list[dict]:
+    with db() as conn:
+        rows = conn.execute(
+            "SELECT * FROM pflege_tipps ORDER BY kategorie, titel"
+        ).fetchall()
+    return [dict(r) for r in rows]
 
 router    = APIRouter()
 MEDIA_DIR = os.getenv("MEDIA_DIR", "/data/media")
@@ -1095,10 +1109,8 @@ async def get_pflege_tipps(dog_id: int, user=Depends(get_current_user)):
         elif any(w in beschr for w in ["schneid", "geschoren", "schere", "clipper"]):
             fell_pflege_art_filter = "schneiden"
 
-    with db() as conn:
-        alle_tipps = conn.execute(
-            "SELECT * FROM pflege_tipps ORDER BY kategorie, titel"
-        ).fetchall()
+    # Statische Tipps aus Cache (1h TTL) – Filterung passiert in-memory
+    alle_tipps = _load_all_pflege_tipps()
 
     # Relevante Tipps: kein Fell-Filter oder passend
     from datetime import date