fix(camera): start layer timelapse for queue/VP-dispatched prints (#1353)

Reporter @Andlar94 ran the external-camera flow on an A1 dispatched via the
  print queue and got no MP4 output even though the log said "Stitching layer
  timelapse for printer 1" after each print. Support bundle confirmed the
  external camera was working (Obico was polling the snapshot URL fine for
  plate detection).

  Root cause: start_session() only ran in the two new-archive paths in
  on_print_start (fallback_archive at main.py:2510 and regular new-archive at
  2600). The expected-archive branch at main.py:1981-2052 — where every
  reprint and every queue/VP-dispatched print lands — updated the existing
  archive row to status=printing but never started a timelapse session.

  So _background_layer_timelapse ran at print complete, called tl_complete(),
  found nothing in _active_sessions, returned None silently, and the wrapper
  at main.py:3917 produced no log message for the no-session case. Every
  print through the queue silently lost its timelapse — likely the reason
  this hasn't been caught before (direct slice-and-send-to-printer prints
  take the new-archive path and work fine).

  Fix: mirror the same start_session() call in the expected-archive branch,
  guarded by the same external_camera_enabled + external_camera_url check the
  other two paths use.

  Also reworded the snapshot URL help text across all 8 locales to make clear
  that timelapse and plate detection each require their own per-printer
  toggle — the URL is just the image source they pull from when active. The
  previous wording read as if filling in the URL was sufficient.

static/index.html

@@ -26,7 +26,7 @@
 
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-    <script type="module" crossorigin src="/assets/index-By5KjUa-.js"></script>
+    <script type="module" crossorigin src="/assets/index-mobeoqIT.js"></script>
     <link rel="stylesheet" crossorigin href="/assets/index-Baw5c3Hn.css">
   </head>
   <body>