Add forecast sparkline graph to point detail panel

- point_detail response includes forecast array (score per valid_time)
- SVG sparkline shows score trend across all forecast hours
- Trend indicator: Improving/Declining/Steady based on first vs last score
- Add covering index (band_mhz, lat, lon, valid_time) INCLUDE (score) for
  point_forecast queries

assets/js/propagation_map_hook.js

@@ -119,6 +119,55 @@ function buildLoadingHTML(detail) {
   </div>`
 }
 
+function buildForecastSvg(forecast) {
+  if (!forecast || forecast.length < 2) return ""
+
+  const w = 240, h = 48, pad = 2
+  const n = forecast.length
+  const now = new Date()
+  const stepX = (w - pad * 2) / (n - 1)
+
+  const points = forecast.map((f, i) => {
+    const x = pad + i * stepX
+    const y = pad + (h - pad * 2) * (1 - f.score / 100)
+    return { x, y, score: f.score, time: new Date(f.time) }
+  })
+
+  const polyline = points.map(p => `${p.x},${p.y}`).join(" ")
+
+  // Find the "now" index
+  const nowIdx = points.reduce((best, p, i) =>
+    Math.abs(p.time - now) < Math.abs(points[best].time - now) ? i : best, 0)
+  const nowPt = points[nowIdx]
+
+  // Trend arrow
+  const firstScore = points[0].score
+  const lastScore = points[points.length - 1].score
+  const diff = lastScore - firstScore
+  let trend = ""
+  if (diff > 5) trend = `<span style="color:#00ffa3;">&#9650; Improving</span>`
+  else if (diff < -5) trend = `<span style="color:#ff4f4f;">&#9660; Declining</span>`
+  else trend = `<span style="color:#ffe566;">&#8594; Steady</span>`
+
+  // Score labels at start and end
+  const startLabel = `<text x="${pad}" y="${h - 2}" font-size="9" fill="rgba(255,255,255,0.5)">${firstScore}</text>`
+  const endLabel = `<text x="${w - pad - 12}" y="${h - 2}" font-size="9" fill="rgba(255,255,255,0.5)">${lastScore}</text>`
+
+  return `
+    <div style="padding:6px 10px;border-top:1px solid rgba(255,255,255,0.15);">
+      <div style="display:flex;justify-content:space-between;align-items:center;margin-bottom:4px;">
+        <span style="font-size:10px;font-weight:700;opacity:0.5;text-transform:uppercase;letter-spacing:0.5px;">Forecast (${n}h)</span>
+        <span style="font-size:11px;">${trend}</span>
+      </div>
+      <svg width="${w}" height="${h}" style="display:block;">
+        <polyline points="${polyline}" fill="none" stroke="#00ffa3" stroke-width="2" stroke-linejoin="round"/>
+        <circle cx="${nowPt.x}" cy="${nowPt.y}" r="3" fill="#fff" stroke="#00ffa3" stroke-width="1.5"/>
+        ${startLabel}
+        ${endLabel}
+      </svg>
+    </div>`
+}
+
 function buildPopupHTML(detail, viewshedLoading) {
   const tier = scoreTier(detail.score)
   const range = rangeEstimate(detail.score, detail)
@@ -167,6 +216,7 @@ function buildPopupHTML(detail, viewshedLoading) {
       <div style="font-size:10px;font-weight:700;opacity:0.5;margin-bottom:4px;text-transform:uppercase;letter-spacing:0.5px;">Analysis</div>
       ${explanations}
     </div>
+    ${detail.forecast ? buildForecastSvg(detail.forecast) : ""}
     ${viewshedStatus}
   </div>`
 }

lib/microwaveprop/propagation.ex

@@ -164,6 +164,24 @@ defmodule Microwaveprop.Propagation do
     Repo.one(from(gs in GridScore, where: gs.band_mhz == ^band_mhz, select: min(gs.valid_time)))
   end
 
+  @doc "Get scores across all forecast hours for a single grid point (for sparkline)."
+  def point_forecast(band_mhz, lat, lon) do
+    step = Grid.step()
+    snapped_lat = Float.round(Float.round(lat / step) * step, 3)
+    snapped_lon = Float.round(Float.round(lon / step) * step, 3)
+
+    Repo.all(
+      from(gs in GridScore,
+        where:
+          gs.band_mhz == ^band_mhz and
+            gs.lat == ^snapped_lat and
+            gs.lon == ^snapped_lon,
+        select: %{valid_time: gs.valid_time, score: gs.score},
+        order_by: [asc: gs.valid_time]
+      )
+    )
+  end
+
   @doc "Get the full score and factors for a specific grid point, snapped to nearest grid."
   def point_detail(band_mhz, lat, lon) do
     step = Grid.step()

lib/microwaveprop_web/live/map_live.ex

@@ -98,8 +98,17 @@ defmodule MicrowavepropWeb.MapLive do
   end
 
   def handle_event("point_detail", %{"lat" => lat, "lon" => lon}, socket) do
-    detail = Propagation.point_detail(socket.assigns.selected_band, lat, lon)
-    {:noreply, push_event(socket, "point_detail", detail || %{})}
+    band = socket.assigns.selected_band
+    detail = Propagation.point_detail(band, lat, lon)
+    forecast = Propagation.point_forecast(band, lat, lon)
+
+    forecast_data =
+      Enum.map(forecast, fn f ->
+        %{time: DateTime.to_iso8601(f.valid_time), score: f.score}
+      end)
+
+    payload = if detail, do: Map.put(detail, :forecast, forecast_data), else: %{}
+    {:noreply, push_event(socket, "point_detail", payload)}
   end
 
   def handle_event("map_bounds", bounds, socket) do

priv/repo/migrations/20260331214714_add_point_forecast_index.exs

@@ -0,0 +1,16 @@
+defmodule Microwaveprop.Repo.Migrations.AddPointForecastIndex do
+  use Ecto.Migration
+
+  def change do
+    # Covers point_forecast query: WHERE band_mhz AND lat AND lon ORDER BY valid_time
+    # INCLUDE score for index-only scan
+    create index(:propagation_scores, [:band_mhz, :lat, :lon, :valid_time],
+             include: [:score],
+             name: :propagation_scores_point_forecast_idx
+           )
+
+    # Covers available_valid_times query: WHERE band_mhz SELECT DISTINCT valid_time
+    # Already covered by propagation_scores_band_mhz_valid_time_index, but adding
+    # the prune query: DELETE WHERE valid_time < cutoff (covered by valid_time_index)
+  end
+end