fix(reader): the Takeout import keeps a later upload, an un-mark and its memory bound

- An ad-hoc request made while its target's run is under way is the run after it: the scheduler
  dropped a second fire of a running id, so a second Takeout file was never imported and its key
  stayed queued until a restart.
- Un-marking or resetting a video is remembered (video_unmarks): an import of an older YouTube view
  no longer marks it watched again; un-marks take the user's Takeout lock.
- One user's failure in the Shorts job's Takeout pass is theirs: the job keeps its own result, the
  others are settled, and a failed lookup spends none of the daily share.
- The upload reads the user's id before giving the read connection back.
- A watched row waits on a discovery video (search or explore) until the catalog keeps it, so a
  mark never pins it against the cleanup jobs.
- The history is decoded a window at a time, a Watch later file over 2 MiB is refused unread, and
  two uploads at once across all users (takeout_server_busy).
- A Watch later list goes in as one presence read and one insert.

frontend/src/i18n/locales/en/errors.json

@@ -254,6 +254,7 @@
     "takeout_unreadable": "This isn't a Takeout file the import reads. Upload watch-history.json (JSON format) or Watch later-videos.csv.",
     "takeout_no_videos": "This file has no videos to import",
     "takeout_busy": "Another of your files is still being uploaded — wait for it to finish",
+    "takeout_server_busy": "Other imports are being received right now — try again in a minute",
     "takeout_cooldown": "You have uploaded many files in the last hour — try again later",
     "takeout_too_many": "That would keep more than {{limit, number}} videos from your export — more than a real one holds",
     "takeout_list_too_long": "This list holds more than {{limit, number}} videos — more than a YouTube list can"

frontend/src/i18n/locales/en/scheduler.json

@@ -188,7 +188,8 @@
     "watch_later_missing": "no longer on YouTube",
     "watch_later_waiting": "Watch later waiting",
     "takeout_watched": "marked watched from Takeout",
-    "takeout_watch_later_added": "put into Watch later from Takeout"
+    "takeout_watch_later_added": "put into Watch later from Takeout",
+    "takeout_failed": "Takeout users left for the next run after an error"
   },
   "skip": {
     "disabled": "disabled",

frontend/src/i18n/locales/hu/errors.json

@@ -254,6 +254,7 @@
     "takeout_unreadable": "Ez nem olyan Takeout-fájl, amit az import olvas. A watch-history.json (JSON formátum) vagy a Watch later-videos.csv fájlt töltsd fel.",
     "takeout_no_videos": "Ebben a fájlban nincs importálható videó",
     "takeout_busy": "Egy másik fájlod feltöltése még folyik — várd meg, amíg befejeződik",
+    "takeout_server_busy": "Épp más importok érkeznek — próbáld újra egy perc múlva",
     "takeout_cooldown": "Az elmúlt órában sok fájlt töltöttél fel — próbáld újra később",
     "takeout_too_many": "Így több mint {{limit, number}} videót őriznénk meg az exportodból — többet, mint amennyi egy valódiban van",
     "takeout_list_too_long": "Ez a lista több mint {{limit, number}} videót tartalmaz — többet, mint amennyi egy YouTube-listán lehet"

frontend/src/i18n/locales/hu/scheduler.json

@@ -188,7 +188,8 @@
     "watch_later_missing": "már nincs a YouTube-on",
     "watch_later_waiting": "a „Megnézem később” listára vár",
     "takeout_watched": "Takeoutból megnézettre jelölve",
-    "takeout_watch_later_added": "Takeoutból a „Megnézem később” listába téve"
+    "takeout_watch_later_added": "Takeoutból a „Megnézem később” listába téve",
+    "takeout_failed": "hiba miatt a következő futásra maradt Takeout-felhasználók"
   },
   "skip": {
     "disabled": "kikapcsolva",