Group the session picker by event instead of one long flat list

The "select session" dropdown in Timing, and the session replay
picker, listed every session across every event in one long flat
list - unwieldy once a club has generated several races' worth of
practice/qualifying/finals sessions. Both now group into <optgroup>s
by event, most recently created event first.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app.js

@@ -1273,6 +1273,7 @@ const TRANSLATIONS = {
     "timing.speaker_panel": "Speaker-panel",
     "timing.speaker_panel_hint": "Dessa växlar slår av/på cues direkt för pågående session och overlay utan att lämna Tidtagning.",
     "timing.select_session": "Välj session",
+    "timing.other_sessions": "Övrigt",
     "timing.set_active": "Sätt aktiv",
     "timing.start": "Starta",
     "timing.stop": "Stoppa",
@@ -2790,6 +2791,7 @@ const TRANSLATIONS = {
     "timing.speaker_panel": "Speaker panel",
     "timing.speaker_panel_hint": "These toggles enable or disable cues live for the current session and overlay without leaving Timing.",
     "timing.select_session": "Select session",
+    "timing.other_sessions": "Other",
     "timing.set_active": "Set Active",
     "timing.start": "Start",
     "timing.stop": "Stop",