Add EDDM size, income, businesses and USPS map link (#17)

## Summary
Closes #17.
- Join USPS EDDM GIS stats onto the carrier-route picker (household size, median income, business count) and link to the official EDDM map.
- GIS miss stays a dash and does not block Find routes; PCM households/cost unchanged.

site/messaging/tests.py

@@ -1,6 +1,7 @@
 from django.contrib.auth import get_user_model
 from django.test import Client, TestCase, override_settings
 from django.urls import reverse
+from unittest.mock import patch
 import json
 
 from contacts.models import Channel, ConsentRecord, Contact, Suppression
@@ -1559,6 +1560,8 @@ class CampaignUtmLinkTests(TestCase):
         self.assertContains(response, "data-utm-qr")
         self.assertContains(response, "utm_campaign")
         self.assertContains(response, reverse("messaging:campaign_short_link"))
+        self.assertContains(response, "https://eddm.usps.com/eddm/select-routes.htm")
+        self.assertContains(response, "Open USPS EDDM map")
 
     def test_detail_shows_tracked_url(self):
         with self.settings(PUBLIC_SITE_URL="https://mkdrealtor.com"):
@@ -1721,6 +1724,12 @@ class CarrierRoutePostcardTests(TestCase):
             email="mail@example.com",
             postal_address=Contact.make_postal_address(line1="9 Main"),
         )
+        self.eddm_patcher = patch(
+            "messaging.providers.postcard.usps_eddm.fetch_eddm_route_stats",
+            return_value={},
+        )
+        self.eddm_stats = self.eddm_patcher.start()
+        self.addCleanup(self.eddm_patcher.stop)
 
     def test_pick_unit_price_uses_break_qty_and_fallback(self):
         from messaging.providers.postcard import pcm as pcm_mod
@@ -1776,6 +1785,49 @@ class CarrierRoutePostcardTests(TestCase):
         self.assertEqual(len(data["routes"]), 2)
         self.assertEqual(data["routes"][0]["cost"], 60.0)
         self.assertEqual(data["mail_class"], "Standard")
+        self.assertEqual(
+            data["eddm_map_url"], "https://eddm.usps.com/eddm/select-routes.htm"
+        )
+
+    def test_quote_search_includes_eddm_demographics(self):
+        self.eddm_stats.return_value = {
+            "60540:C001": {
+                "businesses": 22,
+                "household_size": 2.6,
+                "median_income": 120000,
+                "residential": 108,
+            }
+        }
+        payload = {
+            "listCountID": 11,
+            "recordCount": 120,
+            "breakdown": [
+                {
+                    "breakdownType": "ZipCRRT",
+                    "data": [
+                        {"code": "60540:C001", "text": "NAPERVILLE", "total": 120},
+                    ],
+                }
+            ],
+        }
+        with self.settings(PCM_POSTCARD_PRICE_STANDARD="0.50"):
+            with patch(
+                "messaging.providers.postcard.pcm.design_pricing", return_value=[]
+            ):
+                with patch(
+                    "messaging.providers.postcard.pcm.list_count_zipcode",
+                    return_value=payload,
+                ):
+                    response = self.client.post(
+                        reverse("messaging:postcard_quote"),
+                        data='{"action":"search","zip":"60540","size":"68"}',
+                        content_type="application/json",
+                    )
+        self.assertEqual(response.status_code, 200)
+        row = response.json()["routes"][0]
+        self.assertEqual(row["businesses"], 22)
+        self.assertEqual(row["household_size"], 2.6)
+        self.assertEqual(row["median_income"], 120000)
 
     def test_quote_select_and_save_draft(self):
         from unittest.mock import patch