Flag LiveTrack sessions whose map Garmin no longer serves

Ended sessions past the ~24h Garmin appears to keep a live-track page
around for get verified once at app startup and, once confirmed dead,
flagged so the panel greys them out instead of only failing after a
click. Already-flagged sessions are skipped on later startups so this
doesn't keep re-hitting Garmin for the same dead session.

test/test_livetrack_store.rb

@@ -53,6 +53,35 @@ class LiveTrackStoreTest < Minitest::Test
     assert_includes ids, "old_with_summary"
   end
 
+  def test_stale_ended_finds_old_ended_sessions_but_not_active_recent_or_already_flagged_ones
+    @store.add("old_ended", "tok1")
+    @store.set_summary("old_ended", { "active" => false, "end" => (Time.now.utc - 25 * 60 * 60).iso8601 })
+
+    @store.add("recent_ended", "tok2")
+    @store.set_summary("recent_ended", { "active" => false, "end" => Time.now.utc.iso8601 })
+
+    @store.add("still_active", "tok3")
+    @store.set_summary("still_active", { "active" => true })
+
+    @store.add("already_flagged", "tok4")
+    @store.set_summary("already_flagged", { "active" => false, "end" => (Time.now.utc - 25 * 60 * 60).iso8601 })
+    @store.mark_unavailable("already_flagged")
+
+    ids = @store.stale_ended(24 * 60 * 60).map { |s| s["id"] }
+    assert_equal ["old_ended"], ids
+  end
+
+  def test_mark_unavailable_flags_the_session_without_touching_its_summary
+    @store.add("abc123", "tok-abc")
+    @store.set_summary("abc123", { "session_name" => "Test Ride" })
+
+    @store.mark_unavailable("abc123")
+
+    session = @store.find("abc123")
+    assert_equal false, session["map_available"]
+    assert_equal({ "session_name" => "Test Ride" }, session["summary"])
+  end
+
   def test_data_survives_reload_from_disk
     @store.add("abc123", "tok-abc")
     path = @store.instance_variable_get(:@path)