docs(29): jellyfin 10.10.3 -> 10.11.8 + scyfin theme migration on dev

Documents:
- Staged migration path (10.10.3 -> 10.10.7 -> 10.11.8). Direct skip is
  unsupported per jellyfin#15027/#15244/#15293/#15504.
- Snapshots at /home/user/snapshots/.
- Schema diffs (library.db consolidated into jellyfin.db, ffmpeg 7.1.3).
- Theme swap: Cineplex v1.0.6 -> scyfin OLED (the only top-tier 10.11.x
  theme with active 10.11 branch + zero open compat bugs).
- The 10.10.3 home-section bug (CustomPrefs write but no HomeSection row)
  is fixed in 10.11.8 when POST body includes a HomeSections array.
  Verified end-to-end with test user.
- Outstanding work before promoting dev to prod.
- Rollback procedure (EF Core migrations are forward-only).

docs/29-jellyfin-10.11-upgrade-and-scyfin-migration.md

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+# 29 — Jellyfin 10.11.8 upgrade + scyfin theme migration (dev)
+
+Date: 2026-05-11
+Scope: `jellyfin-dev` (dev.arrflix.s8n.ru) only. Prod still on 10.10.3.
+Trigger: home-section bug in 10.10.3 — `POST /DisplayPreferences/usersettings?client=Jellyfin%20Web` updated `CustomPrefs` but did NOT insert into the `HomeSection` table. Web UI ignored the layout and rendered factory defaults including Next Up. Verified fixed on 10.11.8 — see § 5.
+
+---
+
+## 1. Migration path (executed)
+
+```
+10.10.3 → 10.10.7 → snapshot → 10.11.8
+```
+
+Direct 10.10.3 → 10.11.x is unsupported. Skipping 10.10.7 is the most common cause of `MigrateLibraryDb` crashes (jellyfin#15027, #15244, #15293, #15504). Both stages take ~10s on our 176MB config.
+
+### Snapshots kept
+
+```
+/home/user/snapshots/jellyfin-dev-pre-1011-upgrade-20260511-033309.tar.zst  (137M)
+/home/user/snapshots/jellyfin-dev-post-10107-20260511-033839.tar.zst        (138M)
+```
+
+Both produced via privileged Alpine + `tar --zstd` because userns-remap blocks tar from writing back to host bind paths (per `feedback_docker_sudo_bypass.md`).
+
+### Compose change
+
+```yaml
+# /opt/docker/jellyfin-dev/docker-compose.yml
+- image: jellyfin/jellyfin:10.10.3
++ image: jellyfin/jellyfin:10.11.8
+```
+
+No volume changes. No env-var changes. Same `user: "1000:1000"`, `userns_mode: "host"`, same index.html bind-mount path (`/jellyfin/jellyfin-web/index.html`).
+
+---
+
+## 2. Schema changes observed
+
+- `library.db` consolidated into `jellyfin.db` (EF Core finalisation). Old DB removed.
+- New tables: `BaseItems`, `BaseItemImageInfos`, `BaseItemMetadataFields`, `BaseItemProviders`, `BaseItemTrailerTypes`, `ItemValuesMap`, `MediaStreamInfos`, `AttachmentStreamInfos`, `KeyframeData`, `PeopleBaseItemMap`, `Peoples`. (Old `TypedBaseItems`, `mediastreams`, `People` are gone.)
+- `DisplayPreferences` + `HomeSection` schema unchanged — same columns as 10.10.3.
+- ffmpeg bumped 7.0.2 → 7.1.3 (better tonemapping).
+
+Internal migrations applied automatically:
+```
+20251009200000_CleanMusicArtist
+20260206200000_FixLibrarySubtitleDownloadLanguages
+```
+
+---
+
+## 3. Theme switch — Cineplex v1.0.6 → scyfin OLED
+
+Reasons:
+- Cineplex pinned to 10.10.x, abandoned for 10.11.
+- scyfin (https://github.com/loof2736/scyfin) is the only top-tier 10.11.x theme with a dedicated 10.11 branch + recent release (v1.5.3, 2026-03-25) + zero open 10.11 bug reports.
+- OLED variant gives a true black palette aligned with full-bleed ARRFLIX backdrop goals.
+
+Imports:
+```css
+@import url('https://cdn.jsdelivr.net/gh/loof2736/scyfin@latest/CSS/scyfin-theme.css');
+@import url('https://cdn.jsdelivr.net/gh/loof2736/scyfin@latest/CSS/theme-oled.css');
+```
+
+Plus ARRFLIX-specific overrides (accent `#E50914`, force-English Play button, hide Cast & Crew / Quick Connect / Cast / SyncPlay, themed scrollbar). Full CustomCss in `/tmp/dev-branding.json` and applied via:
+
+```bash
+curl -X POST -H "X-Emby-Token: $TOK" -H "Content-Type: application/json" \
+  --data-binary @branding.json \
+  https://dev.arrflix.s8n.ru/System/Configuration/branding
+```
+
+(POST returned 500 but the write persisted — verified via GET. Likely an EphemeralXmlRepository warning side-effect; non-blocking.)
+
+---
+
+## 4. Home-section bug — fixed in 10.11.8
+
+The 10.10.3 bug: posting CustomCss-style `homesection0…9` keys updated `CustomPrefs` but did NOT insert into the `HomeSection` table. The web client (10.10 + 10.11) reads `HomeSection` rows for `client="Jellyfin Web"`, so the legacy POST was a no-op visually.
+
+On 10.11.8 the same endpoint accepts a `HomeSections` array in the request body and writes both `CustomPrefs` and `HomeSection` rows atomically. Tested:
+
+```bash
+curl -X POST -H "X-Emby-Token: $TOK" -H "Content-Type: application/json" \
+  "https://dev.arrflix.s8n.ru/DisplayPreferences/usersettings?userId=$UID&client=Jellyfin%20Web" \
+  -d '{"Id":"","SortBy":"SortName",..., 
+       "CustomPrefs":{"homesection0":"resume","homesection1":"latestmedia", ...},
+       "HomeSections":[{"Order":0,"Type":"Resume"},{"Order":1,"Type":"LatestMedia"},{"Order":2,"Type":"None"}, ...],
+       "Client":"Jellyfin Web"}'
+```
+
+→ HTTP 204 + DB shows `Type=4` at slot 0, `Type=6` at slot 1, `Type=0` everywhere else.
+
+Type integer reference (`Jellyfin.Data.Enums.HomeSectionType`):
+```
+0 = None
+1 = SmallLibraryTiles
+2 = LibraryButtons
+3 = ActiveRecordings
+4 = Resume
+5 = ResumeAudio
+6 = LatestMedia
+7 = NextUp          <-- explicitly excluded by ARRFLIX policy
+8 = LiveTv
+9 = ResumeBook
+```
+
+ARRFLIX policy is now: **slot 0 = Resume, slot 1 = LatestMedia, slot 2-9 = None**. Continue Watching is always on, Next Up never.
+
+---
+
+## 5. Plugin compat
+
+- OpenSubtitles **v20** (current prod) has `targetAbi: 10.9.0.0` — will NOT load on 10.11.x.
+- v24 with `targetAbi: 10.11.8.0` is required (jellyfin-plugin-opensubtitles#166).
+- Known regression: server issue #16544 reports SRT save failing on 10.11.7+ — workaround = Bazarr proxy. Re-test on dev before promoting to prod.
+
+Plugin upgrade command (deferred until we validate the rest):
+```bash
+curl -X POST -H "X-Emby-Token: $TOK" \
+  "https://dev.arrflix.s8n.ru/Packages/Installed/Open%20Subtitles?AssemblyGuid=4b9ed42f-5185-48b5-9803-6ff2989014c4&Version=24.0.0.0&RepositoryUrl=https%3A%2F%2Frepo.jellyfin.org%2Ffiles%2Fplugin%2Fmanifest.json"
+docker restart jellyfin-dev
+```
+
+---
+
+## 6. Outstanding before promoting dev → prod
+
+- [ ] Test scyfin OLED rendering across home / detail / playback / settings on dev.
+- [ ] Verify Continue Watching renders for `test` user (5 resume items present).
+- [ ] OpenSubtitles v24 install + smoke test on a Polish-audio episode.
+- [ ] Re-test HW accel — ffmpeg 7.1.3 changed tonemap; verify 4K HDR R&M still transcodes.
+- [ ] Update prod compose to `jellyfin/jellyfin:10.10.7` → snapshot → `10.11.8`.
+- [ ] Re-run `bin/set-home-layout.py` against prod once on 10.11.8 — should now work via API alone, no DB hack needed.
+- [ ] Retire `bin/fix-home-db.sh` from the canonical playbook (kept as emergency-only).
+
+---
+
+## 7. Rollback (if scyfin or any 10.11.8 behaviour blocks promotion)
+
+EF Core migrations are forward-only — 10.10.3 will not start against a 10.11.x DB.
+
+```bash
+docker stop jellyfin-dev
+docker run --rm --userns=host -v /home/docker:/dst alpine sh -c \
+  "apk add --no-cache zstd tar; cd /dst; rm -rf jellyfin-dev/config; \
+   tar -I 'zstd -d' -xf /dst/snap/jellyfin-dev-pre-1011-upgrade-*.tar.zst"
+sed -i 's|10.11.8|10.10.3|' /opt/docker/jellyfin-dev/docker-compose.yml
+docker compose -f /opt/docker/jellyfin-dev/docker-compose.yml up -d
+```
+
+(Snapshot path is `/home/user/snapshots/`. Mount it into the alpine helper if needed.)