feat: stream-events log — track title/game changes during live recording

Sibling .events.jsonl alongside each live recording. Default-on
because the cost is one Helix/GQL hit per minute per active
recording — trivial — and the value is real: when seeking inside
a 6h archived stream, "at minute 142 he switched from Just Chatting
to Counter-Strike" is exactly the kind of thing you want answered.

Server:
- new LiveEventTracker (one per active live recording, keyed by
  queue item id). Holds an open file descriptor for the .events.jsonl
  output, last-seen title + game, recording start timestamp.
- start writes a recording_start line with the initial Helix
  metadata snapshot. Stop writes a recording_end line with
  duration + success flag + error message if any.
- Background pollLiveEventsForChanges fires every 60s while at
  least one tracker is active (timer auto-stops when the last
  recording ends so an idle app pays nothing). Per tracker, hits
  getLiveStreamInfo, compares against the cached title/game, emits
  title_change / game_change lines on diff. Game changes also
  trigger a Discord webhook ping when the user has the live-start
  notification enabled — game flips matter more than title micro-
  edits, so we only ping for game.
- JSON Lines format like the chat capture file — a kill mid-stream
  preserves prior data, no need to rewrite.

Wire-up:
- downloadLiveStream starts the tracker after the chat session is
  spun up but before streamlink launches, so the recording_start
  line lands first. Stops it after streamlink exits with the
  result.success flag carried into recording_end. The .events.jsonl
  path is added to outputFiles when it exists so the renderer's
  Open file / Show in folder UI lists it alongside the video and
  chat file.

Renderer / settings:
- new log_stream_events: boolean (default true — it's cheap).
  Settings -> Download card gets a toggle with hint explaining the
  Helix-call-per-minute trade-off.
- AppConfig type, autosave fingerprint, syncSettingsForm,
  applyLanguageToStaticUI, locale strings DE + EN.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.html

@@ -535,6 +535,10 @@
                                 <input type="checkbox" id="captureLiveChatToggle">
                                 <span id="captureLiveChatLabel">Live-Chat waehrend der Aufnahme mitschneiden (.chat.jsonl)</span>
                             </label>
+                            <label style="display:flex; align-items:center; gap:8px; margin-top: 8px;">
+                                <input type="checkbox" id="logStreamEventsToggle" checked>
+                                <span id="logStreamEventsLabel">Stream-Events bei Live-Aufnahmen mitloggen (.events.jsonl)</span>
+                            </label>
                         </div>
                         <div class="form-group">
                             <label id="metadataCacheMinutesLabel">Metadata-Cache (Minuten)</label>