Tesla presence watcher: geofence, ev_presence_obs, 'píchni auto' pobídka

- V095 ems.ev_presence_obs (state/at_home/distance/charging/shift per ~5 min)
- tesla_client: get_vehicle_api_state (jen /vehicles — nebudí), haversine_m
- collector poll_tesla_presence: online → poloha → geofence 150 m vs GPS site;
  přechod pryč→doma + Disconnected → Discord pobídka s aktuálním přebytkem
  (cooldown 2 h); vše logováno pro budoucí dostupnostní statistiku
- 6 testů (haversine, přechody); docs: zákopy reauth procesu (6 bodů)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/services/tesla_client.py

@@ -166,3 +166,33 @@ async def get_charge_state(
             return None
         r.raise_for_status()
         return parse_charge_state(r.json())
+
+
+def haversine_m(lat1: float, lon1: float, lat2: float, lon2: float) -> float:
+    """Vzdálenost dvou GPS bodů v metrech (čisté, testovatelné)."""
+    import math
+
+    r = 6_371_000.0
+    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))
+
+
+async def get_vehicle_api_state(db: asyncpg.Connection, vin: str | None) -> str | None:
+    """Jen state z /vehicles (online/asleep/offline) — NIKDY nebudí auto."""
+    token = await _get_access_token(db)
+    if token is None:
+        return None
+    async with httpx.AsyncClient(
+        timeout=HTTP_TIMEOUT_S, headers={"Authorization": f"Bearer {token}"}
+    ) as client:
+        r = await client.get(f"{API_BASE}/api/1/vehicles")
+        r.raise_for_status()
+        vehicles = r.json().get("response") or []
+        if vin:
+            v = next((x for x in vehicles if x.get("vin") == vin), None)
+        else:
+            v = vehicles[0] if len(vehicles) == 1 else None
+        return str(v["state"]) if v else None