feat(booth): blink the Entry/Exit lights on radar presence (mirror relay 3)

The on-screen Hyrje/Dalje barrier lights were 2-state (green=free / red=busy)
off the camera lane-status only — they couldn't show the radar-only "detected,
not yet confirmed" state that makes the physical button lamp (relay 3) blink.
Now they mirror the lamp's 3-state rule per lane:
  radar present + camera not busy → BLINK green↔red (~1 Hz)
  camera busy                     → SOLID red
  otherwise                       → SOLID green

End-to-end:
- LanePresence (lane-presence.ts): subscribes to deviceEvents.onInput, resolves
  each presence edge to its lane via the new direction-agnostic presenceLaneOf()
  (device-resolve.ts) — entry AND exit, unlike the entry-gated relayForPresence
  the one-car-one-ticket gate uses — and emits a lane-presence {entry,exit} bus
  event on change. Wired in server.ts (start + onClose).
- WS forwards it (hello snapshot + push) into live-store.radar.
- BarrierLight (BoothScreen.tsx) is now 3-state; blinks via the .lane-blink
  keyframe (index.css), which holds solid-red under prefers-reduced-motion.

Same input + same rule as the lamp, so the screen and the post never disagree.

A new test (lane-presence.test.ts) caught a real bug: the first cut reused
relayForPresence, so the EXIT lane never resolved (it's entry-gated) and never
blinked — presenceLaneOf fixes it. Covers entry/exit independence, de-dupe
across several radars on one lane, and ignoring non-presence inputs.

Full workspace build/lint/test green (185 server tests). Updated the
button-light-indicator wiki page ("On-screen twin").

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/index.css

@@ -428,3 +428,30 @@ html.theme-light .btn:hover:not(:disabled) {
 html.theme-light .btn-primary {
   color: #fafaf7;
 }
+
+/* ── Barrier-light blink ────────────────────────────────────────────────────
+   The booth Entry/Exit indicator blinks green↔red (~1 Hz) when the radar/presence
+   input is active but the camera hasn't confirmed a vehicle yet — mirroring the
+   physical button lamp (relay 3). Toggles a CSS var the component maps onto its
+   border / tint / glyph, so green and red alternate every 500 ms. */
+@keyframes lane-blink {
+  0%, 49% { --lane-c: var(--color-term-green); --lane-tint: color-mix(in srgb, var(--color-term-green) 10%, transparent); }
+  50%, 100% { --lane-c: var(--color-term-red); --lane-tint: color-mix(in srgb, var(--color-term-red) 10%, transparent); }
+}
+.lane-blink {
+  animation: lane-blink 1s steps(1, end) infinite;
+  border-color: var(--lane-c);
+  background: var(--lane-tint);
+  color: var(--lane-c);
+}
+@media (prefers-reduced-motion: reduce) {
+  /* No flashing for motion-sensitive users — hold the "attention" (red) state. */
+  .lane-blink {
+    animation: none;
+    --lane-c: var(--color-term-red);
+    --lane-tint: color-mix(in srgb, var(--color-term-red) 10%, transparent);
+    border-color: var(--lane-c);
+    background: var(--lane-tint);
+    color: var(--lane-c);
+  }
+}