Add unique IP count and duplicate detection to sites page

The sites page previously showed total IP count which included duplicates
across multiple sites, leading to inflated numbers. Now displays unique
IP count as the primary metric with duplicate count shown when present.

- Add get_global_ip_stats() method to SiteService for unique/duplicate counts
- Update /api/sites?all=true endpoint to include IP statistics
- Update sites.html to display unique IPs with optional duplicate indicator
- Update API documentation with new response fields

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

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

app/web/services/site_service.py

@@ -228,6 +228,34 @@ class SiteService:
 
         return [self._site_to_dict(site) for site in sites]
 
+    def get_global_ip_stats(self) -> Dict[str, int]:
+        """
+        Get global IP statistics across all sites.
+
+        Returns:
+            Dictionary with:
+                - total_ips: Total count of IP entries (including duplicates)
+                - unique_ips: Count of distinct IP addresses
+                - duplicate_ips: Number of duplicate entries (total - unique)
+        """
+        # Total IP entries
+        total_ips = (
+            self.db.query(func.count(SiteIP.id))
+            .scalar() or 0
+        )
+
+        # Unique IP addresses
+        unique_ips = (
+            self.db.query(func.count(func.distinct(SiteIP.ip_address)))
+            .scalar() or 0
+        )
+
+        return {
+            'total_ips': total_ips,
+            'unique_ips': unique_ips,
+            'duplicate_ips': total_ips - unique_ips
+        }
+
     def bulk_add_ips_from_cidr(self, site_id: int, cidr: str,
                               expected_ping: Optional[bool] = None,
                               expected_tcp_ports: Optional[List[int]] = None,