Add self-hosted routing clients and distance calculator

RoutingConfig loads OSRM/OTP URLs from env vars. OSRM client uses the
/table endpoint for batch NxM distance matrices (walk/cycle). OTP client
uses GraphQL API for transit routes. POI distance calculator orchestrates
both, skipping already-computed distances and reporting progress.

config/routing_config.py

@@ -0,0 +1,52 @@
+"""Routing engine configuration with environment variable loading."""
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass
+from typing import Self
+
+
+@dataclass(frozen=True)
+class RoutingConfig:
+    """Configuration for self-hosted routing engines (OSRM + OTP).
+
+    Attributes:
+        osrm_foot_url: URL for OSRM walking profile instance.
+        osrm_bicycle_url: URL for OSRM cycling profile instance.
+        otp_url: URL for OpenTripPlanner instance.
+        osrm_batch_size: Number of origins per OSRM /table request.
+        otp_max_concurrent: Max concurrent OTP requests.
+    """
+
+    osrm_foot_url: str = "http://osrm-foot:5000"
+    osrm_bicycle_url: str = "http://osrm-bicycle:5000"
+    otp_url: str = "http://otp:8080"
+    osrm_batch_size: int = 50
+    otp_max_concurrent: int = 10
+
+    @classmethod
+    def from_env(cls) -> Self:
+        """Load configuration from environment variables.
+
+        Environment variables:
+            OSRM_FOOT_URL: OSRM walking instance URL (default: http://osrm-foot:5000)
+            OSRM_BICYCLE_URL: OSRM cycling instance URL (default: http://osrm-bicycle:5000)
+            OTP_URL: OpenTripPlanner URL (default: http://otp:8080)
+            OSRM_BATCH_SIZE: Origins per /table request (default: 50)
+            OTP_MAX_CONCURRENT: Max concurrent OTP requests (default: 10)
+        """
+        return cls(
+            osrm_foot_url=os.environ.get("OSRM_FOOT_URL", "http://osrm-foot:5000"),
+            osrm_bicycle_url=os.environ.get("OSRM_BICYCLE_URL", "http://osrm-bicycle:5000"),
+            otp_url=os.environ.get("OTP_URL", "http://otp:8080"),
+            osrm_batch_size=int(os.environ.get("OSRM_BATCH_SIZE", "50")),
+            otp_max_concurrent=int(os.environ.get("OTP_MAX_CONCURRENT", "10")),
+        )
+
+    def get_osrm_url(self, profile: str) -> str:
+        """Get the OSRM URL for a given profile."""
+        if profile == "foot":
+            return self.osrm_foot_url
+        elif profile == "bicycle":
+            return self.osrm_bicycle_url
+        raise ValueError(f"Unknown OSRM profile: {profile}")