fix(race): log initial countdown on start (#356)

## Problem

Starting a race on a contest more than 1 hour away showed no feedback —
`should_notify` only fires at 15-minute intervals, so the first tick
produced no message and the UI appeared frozen during the contest list
fetch.

## Solution

Log the initial countdown immediately after the race timer is set up,
before the first `should_notify` tick fires.

lua/cp/race.lua

@@ -209,6 +209,15 @@ function M.start(platform, contest_id, language)
   race_state.last_refetch = os.time()
   race_state.token = token
 
+  logger.log(
+    ('%s race "%s" starts in %s'):format(
+      display,
+      race_state.contest_name,
+      format_countdown(remaining)
+    ),
+    { level = vim.log.levels.INFO, override = true }
+  )
+
   local timer = vim.uv.new_timer()
   race_state.timer = timer
   timer:start(