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/static/js/pages/walks.js

@@ -628,8 +628,10 @@ window.Page_walks = (() => {
     document.getElementById('wd-photo-input')?.addEventListener('change', async function() {
       if (!this.files.length) return;
       const file = this.files[0];
+      // Client-Side-Kompression vor Upload (HEIC bleibt unverändert)
+      const toUpload = await API.compressImage(file);
       const formData = new FormData();
-      formData.append('file', file);
+      formData.append('file', toUpload);
       try {
         const photo = await API.walks.uploadPhoto(walk.id, formData);
         const grid = document.getElementById('wd-photos-grid');