Add active/inactive/game-time timers to fleet + server pages

Fleet cards and the per-server detail hero now show three live-ticking
timers: Active (since players > 0), Inactive (since server emptied), and
Game (since InitGame in games_sp.log, back-computed from the log's own
MM:SS prefix so it stays accurate across restarts). Anchors are
persisted on `servers` and fanned out via the SSE bus; a single 1s
ticker feeds every card. Idle map cycles are filtered out so the game
timer doesn't flicker.

src/lib/ui/duration.ts

@@ -0,0 +1,27 @@
+/**
+ * Format an elapsed millisecond count as a compact human string:
+ *   < 60s   -> "12s"
+ *   < 1h    -> "5m 23s"
+ *   >= 1h   -> "2h 05m"
+ * Negatives clamp to 0s (clock skew tolerance).
+ */
+export function formatDuration(ms: number): string {
+    if (!Number.isFinite(ms) || ms < 0) ms = 0;
+    const totalSeconds = Math.floor(ms / 1000);
+    if (totalSeconds < 60) return `${totalSeconds}s`;
+    const minutes = Math.floor(totalSeconds / 60);
+    const seconds = totalSeconds % 60;
+    if (minutes < 60) return `${minutes}m ${String(seconds).padStart(2, '0')}s`;
+    const hours = Math.floor(minutes / 60);
+    const mins = minutes % 60;
+    return `${hours}h ${String(mins).padStart(2, '0')}m`;
+}
+
+/**
+ * Convenience: elapsed since an ISO timestamp, formatted. Returns null when
+ * the anchor is null so callers can `{#if}` on it.
+ */
+export function elapsedSince(iso: string | null, now: number): string | null {
+    if (!iso) return null;
+    return formatDuration(now - new Date(iso).getTime());
+}