feat: merge upstream dev branch

- Add Gluetun dynamic VPN-to-HTTP proxy provider
   - Add remote services and authentication system
   - Add country code utilities
   - Add Docker binary detection
   - Update proxy providers

unshackle/core/proxies/nordvpn.py

@@ -1,4 +1,5 @@
 import json
+import random
 import re
 from typing import Optional
 
@@ -46,8 +47,21 @@ class NordVPN(Proxy):
 
         HTTP proxies under port 80 were disabled on the 15th of Feb, 2021:
         https://nordvpn.com/blog/removing-http-proxies
+
+        Supports:
+        - Country code: "us", "ca", "gb"
+        - Country ID: "228"
+        - Specific server: "us1234"
+        - City selection: "us:seattle", "ca:calgary"
         """
         query = query.lower()
+        city = None
+
+        # Check if query includes city specification (e.g., "ca:calgary")
+        if ":" in query:
+            query, city = query.split(":", maxsplit=1)
+            city = city.strip()
+
         if re.match(r"^[a-z]{2}\d+$", query):
             # country and nordvpn server id, e.g., us1, fr1234
             hostname = f"{query}.nordvpn.com"
@@ -64,7 +78,12 @@ class NordVPN(Proxy):
                 # NordVPN doesnt have servers in this region
                 return
 
-            server_mapping = self.server_map.get(country["code"].lower())
+            # Check server_map for pinned servers (can include city)
+            server_map_key = f"{country['code'].lower()}:{city}" if city else country["code"].lower()
+            server_mapping = self.server_map.get(server_map_key) or (
+                self.server_map.get(country["code"].lower()) if not city else None
+            )
+
             if server_mapping:
                 # country was set to a specific server ID in config
                 hostname = f"{country['code'].lower()}{server_mapping}.nordvpn.com"
@@ -76,7 +95,19 @@ class NordVPN(Proxy):
                         f"The NordVPN Country {query} currently has no recommended servers. "
                         "Try again later. If the issue persists, double-check the query."
                     )
-                hostname = recommended_servers[0]["hostname"]
+
+                # Filter by city if specified
+                if city:
+                    city_servers = self.filter_servers_by_city(recommended_servers, city)
+                    if not city_servers:
+                        raise ValueError(
+                            f"No servers found in city '{city}' for country '{country['name']}'. "
+                            "Try a different city or check the city name spelling."
+                        )
+                    recommended_servers = city_servers
+
+                # Pick a random server from the filtered list
+                hostname = random.choice(recommended_servers)["hostname"]
 
         if hostname.startswith("gb"):
             # NordVPN uses the alpha2 of 'GB' in API responses, but 'UK' in the hostname
@@ -95,6 +126,41 @@ class NordVPN(Proxy):
             ):
                 return country
 
+    @staticmethod
+    def filter_servers_by_city(servers: list[dict], city: str) -> list[dict]:
+        """
+        Filter servers by city name.
+
+        The API returns servers with location data that includes city information.
+        This method filters servers to only those in the specified city.
+
+        Args:
+            servers: List of server dictionaries from the NordVPN API
+            city: City name to filter by (case-insensitive)
+
+        Returns:
+            List of servers in the specified city
+        """
+        city_lower = city.lower()
+        filtered = []
+
+        for server in servers:
+            # Each server has a 'locations' list with location data
+            locations = server.get("locations", [])
+            for location in locations:
+                # City data can be in different formats:
+                # - {"city": {"name": "Seattle", ...}}
+                # - {"city": "Seattle"}
+                city_data = location.get("city")
+                if city_data:
+                    # Handle both dict and string formats
+                    city_name = city_data.get("name") if isinstance(city_data, dict) else city_data
+                    if city_name and city_name.lower() == city_lower:
+                        filtered.append(server)
+                        break  # Found a match, no need to check other locations for this server
+
+        return filtered
+
     @staticmethod
     def get_recommended_servers(country_id: int) -> list[dict]:
         """