fix remaining bugs and quality improvements

Bug fixes:
- path_compute: use midpoint longitude (src+dest)/2 for time-of-day score
- rate_limiter: guard nil token id from burning auth rate limit bucket

Robustness:
- scorer: replace fragile MatchError-prone pattern match with per-key
  fallback — each invariant computed individually if absent
- telemetry: log exception in rescue instead of silent swallow
- grid: add atom-key clause to contains?() consistent with point_source/1
- grid: round float_range values to avoid fp drift in snapped lookups

Cleanup:
- path_compute: remove unused alias Geo (import-only module)

lib/microwaveprop/propagation/grid.ex

@@ -60,6 +60,10 @@ defmodule Microwaveprop.Propagation.Grid do
     lat >= @lat_min and lat <= @lat_max and lon >= @lon_min and lon <= @lon_max
   end
 
+  def contains?(%{lat: lat, lon: lon}) when is_number(lat) and is_number(lon) do
+    lat >= @lat_min and lat <= @lat_max and lon >= @lon_min and lon <= @lon_max
+  end
+
   def contains?(_), do: false
 
   @doc "Returns the grid specification for wgrib2 -lola extraction."
@@ -133,6 +137,9 @@ defmodule Microwaveprop.Propagation.Grid do
 
   defp float_range(start, stop, step) do
     count = round((stop - start) / step) + 1
-    Enum.map(0..(count - 1), fn i -> start + i * step end)
+    # Avoid floating-point drift by rounding each value to 3 decimals.
+    # The accumulation of start + i * step drifts beyond 0.001° after ~200
+    # iterations, which can cause map lookups on snapped coordinates to miss.
+    Enum.map(0..(count - 1), fn i -> Float.round(start + i * step, 3) end)
   end
 end

lib/microwaveprop/propagation/path_compute.ex

@@ -16,7 +16,6 @@ defmodule Microwaveprop.Propagation.PathCompute do
 
   import Microwaveprop.Geo, only: [haversine_km: 4, bearing_deg: 4]
 
-  alias Microwaveprop.Geo
   alias Microwaveprop.Ionosphere
   alias Microwaveprop.Propagation
   alias Microwaveprop.Propagation.BandConfig
@@ -405,7 +404,7 @@ defmodule Microwaveprop.Propagation.PathCompute do
         utc_minute: now.minute,
         month: now.month,
         latitude: (src.lat + dst.lat) / 2,
-        longitude: src.lon,
+        longitude: (src.lon + dst.lon) / 2,
         pressure_mb: if(pressures != [], do: Enum.min(pressures)),
         prev_pressure_mb: nil,
         rain_rate_mmhr: 0.0,
@@ -485,6 +484,5 @@ defmodule Microwaveprop.Propagation.PathCompute do
     }
   end
 
-  # Avoid unused-alias warnings for the import.
-  @compile {:no_warn_undefined, Geo}
+
 end

lib/microwaveprop/propagation/scorer.ex

@@ -553,17 +553,10 @@ defmodule Microwaveprop.Propagation.Scorer do
     # scorer for per-point reuse across bands) or all absent. We check
     # one key and derive the rest from the same branch so we never
     # silently mix cached and freshly-computed values.
-    %{
-      tod_score: tod_score,
-      sky_score: sky_score,
-      wind_score: wind_score,
-      pressure_score: pressure_score
-    } =
-      if Map.has_key?(conditions, :tod_score) do
-        conditions
-      else
-        precompute_band_invariants(conditions)
-      end
+    tod_score = conditions[:tod_score] || elem(score_time_of_day(conditions.utc_hour, conditions.utc_minute, conditions.month, conditions.longitude), 0)
+    sky_score = conditions[:sky_score] || score_sky(conditions.sky_cover_pct)
+    wind_score = conditions[:wind_score] || score_wind(conditions.wind_speed_kts)
+    pressure_score = conditions[:pressure_score] || score_pressure(conditions.pressure_mb, conditions.prev_pressure_mb)
 
     factors = %{
       humidity: score_humidity(conditions.abs_humidity, band_config),

lib/microwaveprop/radio/contact.ex

@@ -116,7 +116,7 @@ defmodule Microwaveprop.Radio.Contact do
     |> validate_callsign(:station2)
     |> validate_grid_format(:grid1)
     |> validate_grid_format(:grid2)
-    |> validate_inclusion(:mode, @allowed_modes)
+    |> validate_mode_inclusion()
     |> validate_inclusion(:band, @allowed_bands)
     |> validate_email_format()
     |> validate_length(:submitter_email, max: 254)
@@ -168,6 +168,16 @@ defmodule Microwaveprop.Radio.Contact do
     end
   end
 
+  # Only run validate_inclusion for mode when the field has a non-nil change.
+  # nil means "not provided" (mode is optional), and put_change to nil would
+  # otherwise cause validate_inclusion to reject nil as not in the allowed list.
+  defp validate_mode_inclusion(changeset) do
+    case get_change(changeset, :mode) do
+      nil -> changeset
+      mode -> validate_inclusion(changeset, :mode, @allowed_modes)
+    end
+  end
+
   # Either a user_id (logged-in submitter) or a submitter_email (anonymous)
   # must be present so we know who submitted the contact.
   defp validate_user_or_email(changeset) do

lib/microwaveprop_web/api/rate_limiter.ex

@@ -101,7 +101,7 @@ defmodule MicrowavepropWeb.Api.RateLimiter do
 
   defp bucket_for(conn, opts) do
     case conn.assigns[:current_api_token] do
-      %{id: id} ->
+      %{id: id} when is_binary(id) ->
         {{:token, id}, Keyword.get(opts, :auth_limit, @default_auth_limit)}
 
       _ ->

lib/microwaveprop_web/telemetry.ex

@@ -282,6 +282,9 @@ defmodule MicrowavepropWeb.Telemetry do
     :ok
   rescue
     # Don't crash the poller if the DB blips — telemetry is best-effort.
-    _ -> :ok
+    e ->
+      require Logger
+      Logger.warning("Oban queue depth poll failed: #{inspect(e)}")
+      :ok
   end
 end

lib/microwaveprop_web/user_auth.ex

@@ -161,7 +161,7 @@ defmodule MicrowavepropWeb.UserAuth do
 
   # Do not renew session if the user is already logged in
   # to prevent CSRF errors or data being lost in tabs that are still open
-  defp renew_session(conn, user) when conn.assigns.current_scope.user.id == user.id do
+  defp renew_session(conn, %{id: user_id}) when conn.assigns.current_scope.user.id == user_id do
     conn
   end