fix: resolve test failures from async interference and rate limiting

- hrrr_client_test: async:true => async:false so Req.Test stubs are
  visible in Task.Supervisor.async_stream_nolink worker processes.
- weather_test: add setup blocks to latest_grid_valid_time/0 and
  available_weather_valid_times/0 describe blocks that delete
  is_grid_point=true HrrrProfile rows before each test, preventing
  cross-contamination from other async test modules.
- contact_map_controller_test: call RateLimiter.reset() in setup so
  accumulated ETS counters from prior tests don't trigger 429s.

test/microwaveprop/weather/hrrr_client_test.exs

@@ -1,5 +1,5 @@
 defmodule Microwaveprop.Weather.HrrrClientTest do
-  use ExUnit.Case, async: true
+  use ExUnit.Case, async: false
 
   alias Microwaveprop.Weather.HrrrClient
 

test/microwaveprop/weather_test.exs

@@ -1327,12 +1327,25 @@ defmodule Microwaveprop.WeatherTest do
   end
 
   describe "available_weather_valid_times/0" do
+    # Other async test modules insert HrrrProfile rows with
+    # is_grid_point: true. Wipe them so the "empty DB" assertion
+    # doesn't flake.
+    setup do
+      Repo.delete_all(from(h in HrrrProfile, where: h.is_grid_point == true))
+      :ok
+    end
+
     test "returns an empty list when no scores are stored" do
       assert Weather.available_weather_valid_times() == []
     end
   end
 
   describe "latest_grid_valid_time/0" do
+    setup do
+      Repo.delete_all(from(h in HrrrProfile, where: h.is_grid_point == true))
+      :ok
+    end
+
     test "returns nil when no scores are stored" do
       assert Weather.latest_grid_valid_time() == nil
     end

test/microwaveprop_web/controllers/contact_map_controller_test.exs

@@ -2,12 +2,21 @@ defmodule MicrowavepropWeb.ContactMapControllerTest do
   use MicrowavepropWeb.ConnCase, async: false
 
   alias Microwaveprop.Cache
+  alias MicrowavepropWeb.Api.RateLimiter
 
   setup do
     # The controller caches a gzipped payload under a module-level key —
     # clear it between tests so gzip vs identity requests don't reuse
     # each other's output.
     Cache.invalidate({MicrowavepropWeb.ContactMapController, :gzipped_payload})
+
+    # The controller uses a fixed-window ETS rate limiter. Since every
+    # test request shares the same client IP, accumulated counters from
+    # prior tests (or async tests) can exhaust the bucket and trigger a
+    # 429 before this test even runs. Reset the table per-test so each
+    # describe/3 group starts with a clean slate.
+    RateLimiter.reset()
+
     :ok
   end