Implement story 1.4: location resolution ICAO and address

Adds location.resolve() with ICAO CSV lookup and Nominatim geocoding,
POST /find-location portal route with inline confirmation/error display,
and full test coverage with mocked network calls.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/provisioning/test_portal.py

@@ -1,3 +1,5 @@
+from unittest.mock import patch
+
 import pytest
 
 from planemapper.provisioning.portal import app
@@ -45,3 +47,25 @@ def test_ncsi_redirects_to_index(client) -> None:
 def test_unknown_route_redirects_to_index(client) -> None:
     resp = client.get("/some/random/path")
     assert resp.status_code in (301, 302)
+
+
+def test_find_location_success(client) -> None:
+    mock_resolve = patch(
+        "planemapper.provisioning.portal.location.resolve", return_value=(51.5, -0.1, "London")
+    )
+    with mock_resolve:
+        resp = client.post("/find-location", data={"location": "EGLL", "radius": "100"})
+    assert resp.status_code == 200
+    data = resp.data.decode()
+    assert "London" in data
+    assert "51.5" in data
+
+
+def test_find_location_error(client) -> None:
+    with patch(
+        "planemapper.provisioning.portal.location.resolve",
+        side_effect=ValueError("ICAO code not found — try an address instead"),
+    ):
+        resp = client.post("/find-location", data={"location": "ZZZZ", "radius": "100"})
+    assert resp.status_code == 200
+    assert "ICAO code not found" in resp.data.decode()