fix: countdown hydration mismatch; rate-limit sse-error session refreshes

- suppressHydrationWarning on countdown time text (server second differs
  from client second; first tick corrects)
- sse reconnects attempt a session refresh at most once per minute so a
  flaky stream cannot hammer the refresh endpoint

src/components/countdown.tsx

@@ -53,12 +53,14 @@ export function Countdown({ date, label, color }: CountdownProps) {
   return (
     <Group gap="xs">
       {label && <Text size='sm' fw={500}>{label}:</Text>}
+      {/* Server and client render different seconds; the first client tick corrects it. */}
       <Text
         size='sm'
         fw={600}
         c={isFinalStretch ? 'red' : color}
         ff="monospace"
         className={classes.time}
+        suppressHydrationWarning
       >
         {prefix}
         <span
@@ -66,6 +68,7 @@ export function Countdown({ date, label, color }: CountdownProps) {
           className={`${classes.seconds} ${
             isFinalStretch ? classes.finalTick : classes.tick
           }`}
+          suppressHydrationWarning
         >
           {pad(timeLeft.seconds)}
         </span>