feat: geo location as Google Maps link in Telegram notifications

When signal has geo, show clickable Google Maps link instead of raw
coordinates. Without geo, show "Гео нету". Added parse_mode=HTML
to send_message for link rendering.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/main.py

@@ -223,9 +223,9 @@ async def signal(
 
     ts = datetime.fromtimestamp(body.timestamp / 1000, tz=timezone.utc)
     geo_info = (
-        f"📍 {lat}, {lon} (±{accuracy}м)"
+        f"📍 <a href=\"https://maps.google.com/maps?q={lat},{lon}\">{lat}, {lon}</a> (±{accuracy:.0f}м)"
         if geo
-        else "Без геолокации"
+        else "Гео нету"
     )
     text = (
         f"🚨 Сигнал от {user_name}\n"