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/walks.py

@@ -1,6 +1,6 @@
 """BAN YARO — Gassi-Treffen"""
 
-import math, os, uuid
+import os, uuid
 import httpx
 from datetime import date
 from fastapi import APIRouter, Depends, HTTPException, UploadFile, File
@@ -9,25 +9,13 @@ from typing import Optional, List
 from database import db
 from auth import get_current_user
 from routes.push import send_push_to_user
+from math_utils import haversine_km, haversine_m
 
 MEDIA_DIR = os.getenv("MEDIA_DIR", "/data/media")
 
 router = APIRouter()
 
 
-def _haversine(lat1, lon1, lat2, lon2):
-    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 _haversine_km(lat1, lon1, lat2, lon2):
-    return _haversine(lat1, lon1, lat2, lon2) / 1000
-
-
 # ------------------------------------------------------------------
 # Schemas
 # ------------------------------------------------------------------
@@ -91,7 +79,7 @@ async def list_walks(
 
     # Umkreis-Filter
     if lat is not None and lon is not None:
-        result = [r for r in result if _haversine(lat, lon, r['lat'], r['lon']) <= radius]
+        result = [r for r in result if haversine_m(lat, lon, r['lat'], r['lon']) <= radius]
 
     return result
 
@@ -131,7 +119,7 @@ async def nearby_places(lat: float, lon: float, user=Depends(get_current_user)):
             "SELECT name, typ, lat, lon FROM places WHERE lat IS NOT NULL",
         ).fetchall()
         for p in places:
-            km = _haversine_km(lat, lon, p["lat"], p["lon"])
+            km = haversine_km(lat, lon, p["lat"], p["lon"])
             if km <= 5:
                 results.append({"name": p["name"], "type": p["typ"] or "place",
                                  "lat": p["lat"], "lon": p["lon"],
@@ -142,7 +130,7 @@ async def nearby_places(lat: float, lon: float, user=Depends(get_current_user)):
             "SELECT name, type, lat, lon FROM osm_pois WHERE name IS NOT NULL AND name != ''"
         ).fetchall()
         for p in osm:
-            km = _haversine_km(lat, lon, p["lat"], p["lon"])
+            km = haversine_km(lat, lon, p["lat"], p["lon"])
             if km <= 2:
                 results.append({"name": p["name"], "type": p["type"],
                                  "lat": p["lat"], "lon": p["lon"],
@@ -170,7 +158,7 @@ async def nearby_places(lat: float, lon: float, user=Depends(get_current_user)):
                     elon = el.get("lon") or el.get("center", {}).get("lon")
                     if elat is None or elon is None:
                         continue
-                    km = _haversine_km(lat, lon, elat, elon)
+                    km = haversine_km(lat, lon, elat, elon)
                     if km <= 1:
                         results.append({"name": name, "type": "osm",
                                          "lat": elat, "lon": elon,