feat(contact-detail): render band in MHz below 1 GHz, GHz above

The detail page was hard-coding GHz formatting, so 50/144/222/432/902
rendered as 0.1/0.4/0.9 GHz instead of the MHz labels every amateur
operator actually uses. Switch to MHz when band < 1000, keep GHz for
microwave bands.

Also surface band and mode in the header subtitle so the key QSO
metadata is visible before SRTM/terrain enrichment completes (the
elevation-profile block that previously rendered them is gated on
that enrichment).

lib/microwaveprop_web/live/contact_live/show.ex

@@ -748,7 +748,11 @@ defmodule MicrowavepropWeb.ContactLive.Show do
           {@contact.station1} / {@contact.station2}
         </span>
         <:subtitle>
-          {Calendar.strftime(@contact.qso_timestamp, "%Y-%m-%d %H:%M UTC")}
+          {format_band(@contact.band)}
+          <%= if @contact.mode do %>
+            &middot; {@contact.mode}
+          <% end %>
+          &middot; {Calendar.strftime(@contact.qso_timestamp, "%Y-%m-%d %H:%M UTC")}
           <%= if @contact.flagged_invalid do %>
             <span class="badge badge-error badge-sm ml-2">Flagged Invalid</span>
           <% end %>
@@ -871,7 +875,7 @@ defmodule MicrowavepropWeb.ContactLive.Show do
       <%= if @elevation_profile do %>
         <div class="mb-4">
           <div class="text-sm font-mono mb-2 text-center">
-            {format_band_ghz(@contact.band)} &middot; {@contact.mode} &middot; {format_dist(
+            {format_band(@contact.band)} &middot; {@contact.mode} &middot; {format_dist(
               @elevation_profile.dist_km
             )} &middot; {@contact.grid1 || "—"} &rarr; {@contact.grid2 || "—"}
           </div>
@@ -1464,16 +1468,25 @@ defmodule MicrowavepropWeb.ContactLive.Show do
     "#{String.pad_leading(to_string(whole), 3, "0")}.#{frac}\u00B0"
   end
 
-  defp format_band_ghz(nil), do: "—"
+  defp format_band(nil), do: "—"
 
-  defp format_band_ghz(band) do
+  defp format_band(band) do
     mhz = Decimal.to_float(band)
-    ghz = mhz / 1000
 
-    if ghz == Float.round(ghz, 0) do
-      "#{trunc(ghz)} GHz"
+    if mhz < 1000 do
+      if mhz == Float.round(mhz, 0) do
+        "#{trunc(mhz)} MHz"
+      else
+        "#{:erlang.float_to_binary(mhz, decimals: 1)} MHz"
+      end
     else
-      "#{:erlang.float_to_binary(ghz, decimals: 1)} GHz"
+      ghz = mhz / 1000
+
+      if ghz == Float.round(ghz, 0) do
+        "#{trunc(ghz)} GHz"
+      else
+        "#{:erlang.float_to_binary(ghz, decimals: 1)} GHz"
+      end
     end
   end
 

test/microwaveprop_web/live/contact_live_test.exs

@@ -150,6 +150,34 @@ defmodule MicrowavepropWeb.ContactLiveTest do
       assert render(lv) =~ contact.station1
     end
 
+    # Band display on the detail page: below 1 GHz renders in MHz, at/above
+    # 1 GHz renders in GHz. Amateur band labels match the unit operators use
+    # in QSO logs — you work 432 MHz, you work 10 GHz.
+    test "renders sub-GHz bands in MHz", %{conn: conn} do
+      contact = create_contact(%{band: Decimal.new("432")})
+      {:ok, _lv, html} = live(conn, ~p"/contacts/#{contact.id}")
+      assert html =~ "432 MHz"
+      refute html =~ "0.4 GHz"
+    end
+
+    test "renders 50 MHz in MHz", %{conn: conn} do
+      contact = create_contact(%{band: Decimal.new("50")})
+      {:ok, _lv, html} = live(conn, ~p"/contacts/#{contact.id}")
+      assert html =~ "50 MHz"
+    end
+
+    test "renders GHz bands in GHz", %{conn: conn} do
+      contact = create_contact(%{band: Decimal.new("10000")})
+      {:ok, _lv, html} = live(conn, ~p"/contacts/#{contact.id}")
+      assert html =~ "10 GHz"
+    end
+
+    test "renders 1296 MHz as 1.3 GHz (above the 1 GHz threshold)", %{conn: conn} do
+      contact = create_contact(%{band: Decimal.new("1296")})
+      {:ok, _lv, html} = live(conn, ~p"/contacts/#{contact.id}")
+      assert html =~ "1.3 GHz"
+    end
+
     test "raises for bad UUID", %{conn: conn} do
       assert_raise Ecto.NoResultsError, fn ->
         live(conn, ~p"/contacts/#{Ecto.UUID.generate()}")