Bündel 2: Zentrale Helper für DRY-Cleanup, SW by-v1114

NEUE BACKEND-MODULE:

math_utils.py
- haversine_km(lat1, lon1, lat2, lon2) — Distanz in km
- haversine_m(...) — Convenience-Wrapper in Metern
- bbox_deg_from_km(lat, radius_km) — Bounding-Box-Approximation
  für SQL-Vorfilter (statt Haversine im Python-Loop)

config.py
- DB_PATH, MEDIA_DIR, BREEDER_DOCS_DIR, SCANINPUT_DIR
- API_TIMEOUT_SHORT (5s) / DEFAULT (10s) / LONG (30s)
- HTTP_USER_AGENT, HTTP_HEADERS

errors.py
- not_found(msg), forbidden(msg), bad_request(msg), unauthorized(msg)
- conflict(msg), too_many_requests(msg, retry_after), service_unavailable(msg)
- require_or_404(row, msg) — Convenience-Helper

UI.JS ERWEITERUNGEN:

UI.time erweitert:
- formatDate(d)     → "15.03.2026"
- formatDateTime(d) → "15.03.2026, 14:30"
- weekday(d)        → "Di"
- parseISO(str)     → {year, month, day}

UI.text (neu):
- truncate(str, maxLen, ellipsis='…')
- slug(str) — URL-Slug aus String (mit DE-Umlauten)

UI.money (neu):
- format(value) → "12,34 €" (de-DE, EUR)
- formatWithSuffix(value, '/Jahr')

HAVERSINE-MIGRATION (13 Backend-Routen):
alerts.py, services.py, places.py, events.py, diary.py, playdate.py,
lost.py, poison.py, adoption.py, gassi_zeiten.py, sitting.py, routen.py,
walks.py

- Alle lokalen def _haversine/haversine_km entfernt
- Aufrufe ersetzt durch haversine_km/haversine_m je nach Einheit
- from math_utils import haversine_km|haversine_m in jeder Datei

Tests 19/19 grün.

Hinweis: Migrationen für MEDIA_DIR (19 Stellen), API-Timeouts (12),
Date-Formatter im Frontend (24) und UI.text.truncate (5) sind als
Folge-Sprints möglich. Helper sind verfügbar.

backend/routes/alerts.py

@@ -1,10 +1,10 @@
 """BAN YARO — Nearby Alerts (Giftköder + Vermisste Hunde)"""
-import math
 from datetime import datetime
 from fastapi import APIRouter, Depends
 
 from database import db
 from auth import get_current_user_optional as get_optional_user
+from math_utils import haversine_m, bbox_deg_from_km
 
 router = APIRouter()
 
@@ -12,21 +12,9 @@ _RADIUS_M = 20_000  # 20 km
 _RADIUS_KM = _RADIUS_M / 1000.0
 
 
-def _haversine(lat1: float, lon1: float, lat2: float, lon2: float) -> float:
-    R = 6_371_000
-    p1, p2 = math.radians(lat1), math.radians(lat2)
-    dp = math.radians(lat2 - lat1)
-    dl = math.radians(lon2 - lon1)
-    a = math.sin(dp / 2) ** 2 + math.cos(p1) * math.cos(p2) * math.sin(dl / 2) ** 2
-    return 2 * R * math.asin(math.sqrt(a))
-
-
 def _bbox(lat: float, lon: float, radius_km: float) -> tuple[float, float, float, float]:
     """Bounding-Box-Approximation für lat/lon innerhalb radius_km."""
-    lat_delta = radius_km / 111.0
-    # cos darf bei Polen nicht 0 werden → mit kleinem Minimum absichern
-    cos_lat = max(abs(math.cos(math.radians(lat))), 0.01)
-    lon_delta = radius_km / (111.0 * cos_lat)
+    lat_delta, lon_delta = bbox_deg_from_km(lat, radius_km)
     return (lat - lat_delta, lat + lat_delta, lon - lon_delta, lon + lon_delta)
 
 
@@ -60,7 +48,7 @@ async def nearby_alerts(lat: float, lon: float, user=Depends(get_optional_user))
                 (lat, lon, user["id"])
             )
 
-    has_poison = any(_haversine(lat, lon, r["lat"], r["lon"]) <= _RADIUS_M for r in poisons)
-    has_lost   = any(_haversine(lat, lon, r["lat"], r["lon"]) <= _RADIUS_M for r in lost)
+    has_poison = any(haversine_m(lat, lon, r["lat"], r["lon"]) <= _RADIUS_M for r in poisons)
+    has_lost   = any(haversine_m(lat, lon, r["lat"], r["lon"]) <= _RADIUS_M for r in lost)
 
     return {"poison": has_poison, "lost": has_lost}