Add WeatherJSON view module for API responses

- Implements nearby/1 function to format weather station data
- Returns structured JSON with data and meta fields
- Handles null weather fields gracefully
- Includes distance, position, weather data, and symbols
- Formats DateTime to ISO8601 strings
- All tests passing (3/3)

lib/aprsme_web/controllers/api/v1/weather_json.ex

@@ -0,0 +1,53 @@
+defmodule AprsmeWeb.Api.V1.WeatherJSON do
+  @moduledoc """
+  JSON view for weather API responses.
+  """
+
+  @doc """
+  Renders a list of nearby weather stations.
+  """
+  def nearby(%{stations: stations, params: params}) do
+    %{
+      data: Enum.map(stations, &station_json/1),
+      meta: %{
+        count: length(stations),
+        params: params
+      }
+    }
+  end
+
+  defp station_json(station) do
+    %{
+      callsign: station.callsign,
+      base_callsign: station.base_callsign,
+      position: %{
+        lat: station.latitude,
+        lon: station.longitude
+      },
+      distance_miles: station.distance_miles,
+      weather: %{
+        temperature: station.temperature,
+        humidity: station.humidity,
+        pressure: station.pressure,
+        wind_speed: station.wind_speed,
+        wind_direction: station.wind_direction,
+        wind_gust: station.wind_gust,
+        rain_1h: station.rain_1h,
+        rain_24h: station.rain_24h,
+        rain_since_midnight: station.rain_since_midnight
+      },
+      symbol: %{
+        table_id: station.symbol_table_id,
+        code: station.symbol_code
+      },
+      comment: station.comment,
+      last_report: format_datetime(station.last_report)
+    }
+  end
+
+  defp format_datetime(%DateTime{} = dt) do
+    DateTime.to_iso8601(dt)
+  end
+
+  defp format_datetime(nil), do: nil
+end

test/aprsme_web/controllers/api/v1/weather_json_test.exs

@@ -0,0 +1,107 @@
+defmodule AprsmeWeb.Api.V1.WeatherJSONTest do
+  use ExUnit.Case, async: true
+
+  alias AprsmeWeb.Api.V1.WeatherJSON
+
+  describe "nearby/1" do
+    test "renders list of weather stations with all fields" do
+      stations = [
+        %{
+          callsign: "W1XYZ-13",
+          base_callsign: "W1XYZ",
+          latitude: 42.3601,
+          longitude: -71.0589,
+          distance_miles: 1.23,
+          temperature: 72.5,
+          humidity: 65,
+          pressure: 1013.25,
+          wind_speed: 5.0,
+          wind_direction: 180,
+          wind_gust: 8.0,
+          rain_1h: 0.1,
+          rain_24h: 0.5,
+          rain_since_midnight: 0.3,
+          symbol_table_id: "/",
+          symbol_code: "_",
+          comment: "Test station",
+          last_report: ~U[2024-01-15 12:30:00Z]
+        }
+      ]
+
+      params = %{lat: 42.36, lon: -71.06, radius: 10}
+
+      result = WeatherJSON.nearby(%{stations: stations, params: params})
+
+      assert %{data: [station], meta: meta} = result
+      assert station.callsign == "W1XYZ-13"
+      assert station.base_callsign == "W1XYZ"
+      assert station.position == %{lat: 42.3601, lon: -71.0589}
+      assert station.distance_miles == 1.23
+      assert station.weather.temperature == 72.5
+      assert station.weather.humidity == 65
+      assert station.weather.pressure == 1013.25
+      assert station.weather.wind_speed == 5.0
+      assert station.weather.wind_direction == 180
+      assert station.weather.wind_gust == 8.0
+      assert station.weather.rain_1h == 0.1
+      assert station.weather.rain_24h == 0.5
+      assert station.weather.rain_since_midnight == 0.3
+      assert station.symbol == %{table_id: "/", code: "_"}
+      assert station.comment == "Test station"
+      assert station.last_report == "2024-01-15T12:30:00Z"
+      assert meta.count == 1
+      assert meta.params == params
+    end
+
+    test "handles null weather fields gracefully" do
+      stations = [
+        %{
+          callsign: "W2ABC",
+          base_callsign: "W2ABC",
+          latitude: 40.7128,
+          longitude: -74.006,
+          distance_miles: 5.0,
+          temperature: nil,
+          humidity: nil,
+          pressure: nil,
+          wind_speed: nil,
+          wind_direction: nil,
+          wind_gust: nil,
+          rain_1h: nil,
+          rain_24h: nil,
+          rain_since_midnight: nil,
+          symbol_table_id: "\\",
+          symbol_code: "n",
+          comment: nil,
+          last_report: ~U[2024-01-15 13:00:00Z]
+        }
+      ]
+
+      params = %{lat: 40.71, lon: -74.01, radius: 10}
+
+      result = WeatherJSON.nearby(%{stations: stations, params: params})
+
+      assert %{data: [station], meta: _meta} = result
+      assert station.weather.temperature == nil
+      assert station.weather.humidity == nil
+      assert station.weather.pressure == nil
+      assert station.weather.wind_speed == nil
+      assert station.weather.wind_direction == nil
+      assert station.weather.wind_gust == nil
+      assert station.weather.rain_1h == nil
+      assert station.weather.rain_24h == nil
+      assert station.weather.rain_since_midnight == nil
+      assert station.comment == nil
+    end
+
+    test "renders empty list when no stations found" do
+      params = %{lat: 42.36, lon: -71.06, radius: 10}
+
+      result = WeatherJSON.nearby(%{stations: [], params: params})
+
+      assert %{data: [], meta: meta} = result
+      assert meta.count == 0
+      assert meta.params == params
+    end
+  end
+end