Fix IP geolocation service: change to HTTPS and add IP validation

geolocation.py

 import asyncio
 import httpx
+import ipaddress
 from typing import Dict, Optional
 
 # Global cache for IP -> country mappings
@@ -7,15 +8,22 @@ _ip_country_cache: Dict[str, Optional[str]] = {}
 
 async def get_ip_country(ip: str) -> Optional[str]:
     """Get country code for IP address using ipapi.co, with caching.
-    
+
     Returns country code (e.g., 'IL') or None if failed.
     """
+    # Validate IP address format
+    try:
+        ipaddress.ip_address(ip)
+    except ValueError:
+        _ip_country_cache[ip] = None
+        return None
+
     if ip in _ip_country_cache:
         return _ip_country_cache[ip]
     
     try:
         async with httpx.AsyncClient(timeout=5.0) as client:
-            response = await client.get(f"http://ipapi.co/{ip}/country/")
+            response = await client.get(f"https://ipapi.co/{ip}/country/")
             if response.status_code == 200:
                 country = response.text.strip().upper()
                 _ip_country_cache[ip] = country