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/diary.py

@@ -1,6 +1,6 @@
 """BAN YARO — Tagebuch Routes"""
 
-import os, uuid, json, math, logging
+import os, uuid, json, math, logging, asyncio
 from fastapi import APIRouter, Depends, HTTPException, UploadFile, File
 from pydantic import BaseModel
 from typing import Optional
@@ -684,7 +684,13 @@ async def upload_media(dog_id: int, entry_id: int,
         validate_upload(raw_data, file.filename or "")
     except ValueError as e:
         raise HTTPException(415, str(e))
-    raw_data, ext = convert_media(raw_data, file.filename or "")
+
+    # Blockierende Bild-/Video-Konvertierung in Threadpool auslagern,
+    # damit der Event-Loop für andere Requests frei bleibt.
+    loop = asyncio.get_event_loop()
+    raw_data, ext = await loop.run_in_executor(
+        None, lambda: convert_media(raw_data, file.filename or "")
+    )
     if not ext:
         ext = ".jpg"
     filename   = f"diary_{entry_id}_{uuid.uuid4().hex[:8]}{ext}"
@@ -692,17 +698,21 @@ async def upload_media(dog_id: int, entry_id: int,
     media_type = _guess_media_type(ct, file.filename or "")
     os.makedirs(os.path.dirname(path), exist_ok=True)
 
-    with open(path, "wb") as f:
-        f.write(raw_data)
+    def _write_bytes(p: str, data: bytes) -> None:
+        with open(p, "wb") as f:
+            f.write(data)
+
+    await loop.run_in_executor(None, lambda: _write_bytes(path, raw_data))
 
     if media_type == "video":
-        extract_video_thumb(path)
+        await loop.run_in_executor(None, lambda: extract_video_thumb(path))
     elif media_type == "image":
-        preview_bytes = generate_preview(raw_data, ext)
+        preview_bytes = await loop.run_in_executor(
+            None, lambda: generate_preview(raw_data, ext)
+        )
         if preview_bytes:
             preview_path = os.path.splitext(path)[0] + "_preview.webp"
-            with open(preview_path, "wb") as f:
-                f.write(preview_bytes)
+            await loop.run_in_executor(None, lambda: _write_bytes(preview_path, preview_bytes))
 
     media_url = f"/media/diary/{filename}"
 
@@ -710,8 +720,8 @@ async def upload_media(dog_id: int, entry_id: int,
     exif_gps  = None
     img_size  = None
     if media_type == "image":
-        exif_gps = extract_gps_from_exif(raw_data)
-        img_size = get_image_size(raw_data)
+        exif_gps = await loop.run_in_executor(None, lambda: extract_gps_from_exif(raw_data))
+        img_size = await loop.run_in_executor(None, lambda: get_image_size(raw_data))
 
     with db() as conn:
         # sort_order = nächste freie Position