Sprint 7: Gassi-Treffen — Meetup-Feature komplett

- Backend: walks.py mit allen Endpoints (CRUD, join/leave, Haversine-Filter)
- DB: walks, walk_participants, walk_participant_dogs Tabellen (bereits in database.py)
- Frontend: walks.js — Liste/Karte-Toggle, Heute/Demnächst-Gruppierung, Detail-Modal
  mit Teilnehmerliste, Beitreten/Verlassen, Erstellen/Bearbeiten-Formulare
- CSS: Walks-Komponenten (Card, Date-Badge, Spots-Anzeige, Map-View)
- api.js: walks-Abschnitt (list, get, create, update, cancel, join, leave)
- SW-Cache: by-v20 → by-v21

backend/main.py

@@ -59,6 +59,7 @@ from routes.ki         import router as ki_router
 from routes.tieraerzte import router as tieraerzte_router
 from routes.places     import router as places_router
 from routes.routen     import router as routen_router
+from routes.walks      import router as walks_router
 
 app.include_router(auth_router,       prefix="/api/auth",       tags=["Auth"])
 app.include_router(dogs_router,       prefix="/api/dogs",       tags=["Hunde"])
@@ -70,6 +71,7 @@ app.include_router(ki_router,         prefix="/api/ki",         tags=["KI"])
 app.include_router(tieraerzte_router, prefix="/api/tieraerzte", tags=["Tierärzte"])
 app.include_router(places_router,     prefix="/api/places",     tags=["Orte"])
 app.include_router(routen_router,     prefix="/api/routes",     tags=["Routen"])
+app.include_router(walks_router,      prefix="/api/walks",      tags=["Gassi-Treffen"])
 
 
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