feat: Add real-time visitor map with IP geolocation

- Add latitude/longitude columns to visitor_logs model
- Update visitor_service to fetch and store coordinates from ip-api.com
- Add /admin/map-data API endpoint for map visualization
- Create VisitorMap component using Leaflet/OpenStreetMap
- Integrate map into visitor-stats admin page
- 30-second auto-refresh with animation for new visitors
- Color-coded markers (red: active, blue: recent)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/models/visitor.py

@@ -1,7 +1,7 @@
 """
 Visitor tracking models for analytics
 """
-from sqlalchemy import Column, Integer, String, DateTime, Text, Index
+from sqlalchemy import Column, Integer, String, DateTime, Text, Index, Float
 from sqlalchemy.sql import func
 from ..database import Base
 
@@ -41,6 +41,8 @@ class VisitorLog(Base):
     country_code = Column(String(5), nullable=True)
     city = Column(String(100), nullable=True)
     region = Column(String(100), nullable=True)
+    latitude = Column(Float, nullable=True)
+    longitude = Column(Float, nullable=True)
 
     # UTM parameters
     utm_source = Column(String(100), nullable=True)