Sprint 8: Events + Hundesitting

Events:
- Backend events.py: CRUD, Typen (ausstellung/training/treffen/markt/wettkampf/sonstiges)
  Haversine-Filter, Monats-Gruppierung in der Liste
- Frontend events.js: Liste/Karte-Toggle, Typ-Filter-Chips, farbige Marker,
  Detail-Modal, Erstellen/Bearbeiten-Formular mit GPS-Button

Hundesitting:
- Backend sitting.py: Sitter-Profile (create/update/me), Anfragen (send/accept/decline/cancel),
  Inbox für Sitter, Haversine-Sortierung, Service-Filter
- Frontend sitting.js: 3 Tabs (Suchen/Profil/Anfragen), Sitter-Karten mit Distanz,
  Detail-Modal + Anfrage-Formular, Profil-Verwaltung

DB: events, sitters, sitting_requests Tabellen hinzugefügt
SW-Cache: by-v21 → by-v22

backend/static/js/api.js

@@ -207,6 +207,39 @@ const API = (() => {
     leave(id)         { return del(`/walks/${id}/join`); },
   };
 
+  // ----------------------------------------------------------
+  // EVENTS
+  // ----------------------------------------------------------
+  const events = {
+    list(params = {}) {
+      const q = new URLSearchParams(params).toString();
+      return get(`/events${q ? '?' + q : ''}`);
+    },
+    get(id)          { return get(`/events/${id}`); },
+    create(data)     { return post('/events', data); },
+    update(id, data) { return patch(`/events/${id}`, data); },
+    delete(id)       { return del(`/events/${id}`); },
+  };
+
+  // ----------------------------------------------------------
+  // SITTING
+  // ----------------------------------------------------------
+  const sitting = {
+    list(lat = null, lon = null, radius = 30000, service = null) {
+      const p = new URLSearchParams({ radius });
+      if (lat !== null) { p.set('lat', lat); p.set('lon', lon); }
+      if (service)      { p.set('service', service); }
+      return get(`/sitting?${p}`);
+    },
+    me()             { return get('/sitting/me'); },
+    create(data)     { return post('/sitting', data); },
+    updateMe(data)   { return patch('/sitting/me', data); },
+    requests()       { return get('/sitting/requests'); },
+    inbox()          { return get('/sitting/inbox'); },
+    sendRequest(data){ return post('/sitting/requests', data); },
+    updateRequest(id, status) { return patch(`/sitting/requests/${id}`, { status }); },
+  };
+
   // ----------------------------------------------------------
   // WETTER
   // ----------------------------------------------------------
@@ -284,7 +317,7 @@ const API = (() => {
   return {
     get, post, put, patch, del, upload,
     auth, dogs, diary, health, tieraerzte, poison,
-    places, routes, walks, weather, push,
+    places, routes, walks, events, sitting, weather, push,
     subscribeToPush, getLocation,
     APIError,
   };