feat(keys): Back returns focus to the item a view was opened from; "Feed" everywhere; every backend id named

Owner answers to the E11 S5 raises (2026-09-13): 1 → A, 2 → "Feed" in every language, 3 → translate the
proxy label and fix every config key missing in BOTH languages ("maintenance", "tmdb" — old bugs).

Focus across a view change (1-A). Opening a Plex title from Home's rail, a channel from the Channels
table or a title from a Plex grid switches the page or the sub-view, which unmounts the list; Back used
to hand focus to <body>, so the next `j` started over at the top. The YouTube player (an overlay)
already restored onto the card.
- `lib/listNav`: `navPosition()` (list's place in reading order, the page's list count, item index)
  and `restoreNavPosition()`: focuses the item once the page has as many lists on screen as when it was
  left, polls on a timer (a hidden tab runs no animation frames), gives up after 2 s or at once when
  something already holds focus, focuses without scrolling (the scroll restore owns the position).
- `lib/history`: `rememberNavPosition()` stamps `sfNav` onto the entry being left and returns the state
  without it (a new entry must not inherit it); one popstate listener restores and spends the stamp,
  so a later landing on the same entry (an overlay closing over it) cannot pull focus to an old item.
- Called before every view push: `setPage`, `openChannel`, `enterYtSearch`, `useHistorySubview.open`,
  the Channels tab push. `navPosition.wiring.contract.test` fails on any `history.pushState(` without
  it (the overlay stack's own push is the one exemption).

"Feed" (2). The module is "Feed" in both languages: every "hírfolyam" in the Hungarian UI (≈45 strings,
suffixed: Feedből, Feeded, Feedben…) and the prose "feed" in English that means the module ("your
Feed", "Hide from Feed"); "RSS feed" keeps its meaning. The welcome email says it too.

Backend ids without a name (3). The Configuration page showed `maintenance`, `tmdb`,
`maintenance_revalidate_batch`, `download_upload_max_bytes`, `audit_retention_days`, `plex_overlay_map`,
`tmdb_api_key` and `tmdb_language` as raw identifiers — the lookup falls back to the id, and the i18n
parity test stayed green because both languages missed the same keys. Added labels + hints (EN/HU),
the two groups (and their tab order), the missing `scheduler.jobDesc.demo_reset`, removed the stale
`plex_sync_interval_min` field, and "YouTube API kimenő proxy". `i18n/backendIds.contract.test` reads
`sysconfig.SPECS`, `scheduler.JOB_INTERVALS` and the audit/quota action enums from the backend sources
and fails on an id without its name in either language, or a name left for an id the backend dropped.

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

@@ -54,9 +54,9 @@
     "title": "Account",
     "youtubeAccess": "YouTube access",
     "youtubeAccessIntro": "Sign-in only shares your name and email. YouTube access is granted separately, below — each is optional and revocable anytime in your Google Account.",
-    "readTitle": "Read subscriptions (your feed)",
-    "readGrantedHint": "Granted. Siftlode reads the channels you follow to build your feed. It never changes your YouTube account with this.",
-    "readEnableHint": "Read-only access to your subscriptions — required to build your feed. Siftlode can't modify anything with it.",
+    "readTitle": "Read subscriptions (your Feed)",
+    "readGrantedHint": "Granted. Siftlode reads the channels you follow to build your Feed. It never changes your YouTube account with this.",
+    "readEnableHint": "Read-only access to your subscriptions — required to build your Feed. Siftlode can't modify anything with it.",
     "writeTitle": "Unsubscribe (write)",
     "writeGrantedHint": "Granted. You can unsubscribe from channels on YouTube from inside Siftlode. It only writes when you ask it to.",
     "writeEnableHint": "Lets Siftlode unsubscribe from channels on YouTube for you. Optional — skip it to stay read-only.",
@@ -76,7 +76,7 @@
       "title": "Google account",
       "connected": "Connected",
       "connectedHint": "Your Google account is linked. You can sign in with Google and grant YouTube access below.",
-      "connectHint": "Link a Google account to sign in with Google and to enable YouTube access for your feed.",
+      "connectHint": "Link a Google account to sign in with Google and to enable YouTube access for your Feed.",
       "connect": "Connect Google",
       "linked": "Google account linked.",
       "conflict": "That Google account is already linked to a different Siftlode account.",