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/playdate.py

@@ -1,30 +1,17 @@
 """BAN YARO — Playdate-Matching"""
 
-import math
 import logging
 from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel
 from typing import Optional
 from database import db
 from auth import get_current_user
+from math_utils import haversine_km
 
 router = APIRouter()
 logger = logging.getLogger(__name__)
 
 
-# ------------------------------------------------------------------
-# Haversine
-# ------------------------------------------------------------------
-def _haversine(lat1: float, lon1: float, lat2: float, lon2: float) -> float:
-    R = 6371.0
-    dlat = math.radians(lat2 - lat1)
-    dlon = math.radians(lon2 - lon1)
-    a = (math.sin(dlat / 2) ** 2
-         + math.cos(math.radians(lat1)) * math.cos(math.radians(lat2))
-         * math.sin(dlon / 2) ** 2)
-    return R * 2 * math.asin(math.sqrt(a))
-
-
 def _calc_alter(geburtstag: Optional[str]) -> Optional[str]:
     """Gibt lesbares Alter zurück z.B. '2 Jahre' oder '5 Monate'."""
     if not geburtstag:
@@ -107,7 +94,7 @@ async def nearby(lat: float, lon: float, radius: int = 10,
 
     result = []
     for r in rows:
-        dist = _haversine(lat, lon, r["lat"], r["lon"])
+        dist = haversine_km(lat, lon, r["lat"], r["lon"])
         if dist <= radius:
             result.append({
                 "listing_id":    r["listing_id"],