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/wiki.py

@@ -10,6 +10,7 @@ from pydantic import BaseModel
 from database import db
 from auth import get_current_user, get_current_user_optional
 from ratelimit import check as rl_check, block_ip
+from cache import ttl_cache
 
 logger     = logging.getLogger(__name__)
 MEDIA_DIR   = os.getenv("MEDIA_DIR", "/data/media")
@@ -81,16 +82,34 @@ def _quiz_score(rasse: dict, params: dict) -> int:
 
 
 # ------------------------------------------------------------------
-# GET /api/wiki/stats — Seed-Status
+# GET /api/wiki/stats — Seed-Status (1h TTL-Cache, statische Anzahl)
 # ------------------------------------------------------------------
-@router.get("/stats")
-async def get_stats():
+@ttl_cache(ttl=3600)
+def _wiki_stats() -> dict:
     with db() as conn:
         row = conn.execute("SELECT COUNT(*) as total FROM wiki_rassen").fetchone()
         total = row["total"] if row else 0
     return {"total_breeds": total, "seeded": total > 0}
 
 
+@router.get("/stats")
+async def get_stats():
+    return _wiki_stats()
+
+
+# ------------------------------------------------------------------
+# Gruppen-Liste für Filter-Dropdown – statisch, 1h TTL-Cache
+# ------------------------------------------------------------------
+@ttl_cache(ttl=3600)
+def _wiki_gruppen() -> list[str]:
+    with db() as conn:
+        rows = conn.execute(
+            "SELECT DISTINCT gruppe FROM wiki_rassen "
+            "WHERE gruppe IS NOT NULL ORDER BY gruppe"
+        ).fetchall()
+    return [r["gruppe"] for r in rows]
+
+
 # ------------------------------------------------------------------
 # GET /api/wiki/rassen — alle Rassen (Übersicht, paginiert)
 # ------------------------------------------------------------------
@@ -134,15 +153,13 @@ async def get_rassen(
             SELECT COUNT(*) as total FROM wiki_rassen {where}
         """, args).fetchone()
 
-        # Alle Gruppen für Filter-Dropdown
-        gruppen_rows = conn.execute(
-            "SELECT DISTINCT gruppe FROM wiki_rassen WHERE gruppe IS NOT NULL ORDER BY gruppe"
-        ).fetchall()
+    # Alle Gruppen für Filter-Dropdown (gecached, 1h TTL)
+    gruppen = _wiki_gruppen()
 
     return {
         "breeds":  [dict(r) for r in rows],
         "total":   count_row["total"] if count_row else 0,
-        "gruppen": [r["gruppe"] for r in gruppen_rows],
+        "gruppen": gruppen,
     }