feat(video, settings, docs): add muted playback, nested Settings tabs, merge holidays tab; bump 2025.1.0-alpha.11

API/DB: add Event.muted with full CRUD wiring (Alembic migration), persist/return with autoplay/loop/volume
Dashboard: per‑event video options (autoplay/loop/volume/muted) with system defaults; Settings → Events → Videos defaults
Settings UX: nested tabs with controlled selection; Academic Calendar: merge “Schulferien Import”+“Liste” into “📥 Import & Liste”
Docs: update README and copilot-instructions (video payload, streaming 206, defaults keys); update program-info.json changelog; bump version to 2025.1.0‑alpha.11

.github/copilot-instructions.md

@@ -28,6 +28,7 @@ Small multi-service digital signage app (Flask API, React dashboard, MQTT schedu
 - `server/routes/events.py` — event CRUD and recurrence handling
 - `dashboard/src/components/CustomEventModal.tsx` — event creation UI
 - `dashboard/src/media.tsx` — FileManager / upload settings
+ - `dashboard/src/settings.tsx` — settings UI (nested tabs; system defaults for presentations and videos)
 
 
 ## Big picture
@@ -47,6 +48,11 @@ Small multi-service digital signage app (Flask API, React dashboard, MQTT schedu
   - Dashboard: UI updated to allow selecting uploaded videos for events and to specify autoplay/loop/volume. File upload settings were increased (maxFileSize raised) and the client now validates video duration (max 10 minutes) before upload.
   - FileManager: uploads compute basic metadata and enqueue conversions for office formats as before; video uploads now surface size and are streamable via the new endpoint.
 
+  - Event model & API (new): Added `muted` (Boolean) for video events; create/update and GET endpoints accept, persist, and return `muted` alongside `autoplay`, `loop`, and `volume`.
+  - Dashboard — Settings: Settings page refactored to nested tabs; added Events → Videos defaults (autoplay, loop, volume, mute) backed by system settings keys (`video_autoplay`, `video_loop`, `video_volume`, `video_muted`).
+  - Dashboard — Events UI: CustomEventModal now exposes per-event video `muted` and initializes all video fields from system defaults when creating a new event.
+  - Dashboard — Academic Calendar: Merged “School Holidays Import” and “List” into a single “📥 Import & Liste” tab; nested tab selection is persisted with controlled `selectedItem` state to avoid jumps.
+
   Note: these edits are intentionally backwards-compatible — if the probe fails, the scheduler still emits the stream URL and the client should fallback to a direct play attempt or request richer metadata when available.
 
 ## Service boundaries & data flow
@@ -76,7 +82,14 @@ Small multi-service digital signage app (Flask API, React dashboard, MQTT schedu
     - `presentation_page_progress` ("true"/"false", default "true")
     - `presentation_auto_progress` ("true"/"false", default "true")
     Seeded in `server/init_defaults.py` if missing.
+  - Video defaults (system-wide):
+    - `video_autoplay` ("true"/"false", default "true")
+    - `video_loop` ("true"/"false", default "true")
+    - `video_volume` (0.0–1.0, default "0.8")
+    - `video_muted` ("true"/"false", default "false")
+    Used as initial values when creating new video events; editable per event.
   - Events: Added `page_progress` (Boolean) and `auto_progress` (Boolean) for presentation behavior per event.
+  - Event (video fields): `event_media_id`, `autoplay`, `loop`, `volume`, `muted`.
   - WebUntis URL: WebUntis uses the existing Vertretungsplan/Supplement-Table URL (`supplement_table_url`). There is no separate `webuntis_url` setting; use `GET/POST /api/system-settings/supplement-table`.
 
 - Conversions:
@@ -137,8 +150,8 @@ Small multi-service digital signage app (Flask API, React dashboard, MQTT schedu
 - Settings page (`dashboard/src/settings.tsx`):
   - Structure: Syncfusion TabComponent with role-gated tabs
     - 📅 Academic Calendar (all users)
-      - School Holidays: CSV/TXT import and list
-      - Academic Periods: select and set active period (uses `/api/academic_periods` routes)
+      - 📥 Import & Liste: CSV/TXT import and list combined
+      - 🗂️ Perioden: select and set active period (uses `/api/academic_periods` routes)
     - 🖥️ Display & Clients (admin+)
       - Default Settings: placeholders for heartbeat, screenshots, defaults
       - Client Configuration: quick links to Clients and Groups pages
@@ -148,11 +161,13 @@ Small multi-service digital signage app (Flask API, React dashboard, MQTT schedu
     - 🗓️ Events (admin+)
       - WebUntis / Vertretungsplan: system-wide supplement table URL with enable/disable, save, and preview; persists via `/api/system-settings/supplement-table`
       - Presentations: general defaults for slideshow interval, page-progress, and auto-progress; persisted via `/api/system-settings` keys (`presentation_interval`, `presentation_page_progress`, `presentation_auto_progress`). These defaults are applied when creating new presentation events (the custom event modal reads them and falls back to per-event values when editing).
-      - Other event types (website, video, message, other): placeholders for defaults
+      - Videos: system-wide defaults for `autoplay`, `loop`, `volume`, and `muted`; persisted via `/api/system-settings` keys (`video_autoplay`, `video_loop`, `video_volume`, `video_muted`). These defaults are applied when creating new video events (the custom event modal reads them and falls back to per-event values when editing).
+      - Other event types (website, message, other): placeholders for defaults
     - ⚙️ System (superadmin)
       - Organization Info and Advanced Configuration placeholders
   - Role gating: Admin/Superadmin tabs are hidden if the user lacks permission; System is superadmin-only
   - API clients use relative `/api/...` URLs so Vite dev proxy handles requests without CORS issues. The settings UI calls are centralized in `dashboard/src/apiSystemSettings.ts`.
+  - Nested tabs: implemented as controlled components using `selectedItem` with stateful handlers to prevent sub-tab resets during updates.
 
 - User dropdown technical notes:
   - Dependencies: `@syncfusion/ej2-react-splitbuttons` and `@syncfusion/ej2-splitbuttons` must be installed.
@@ -189,7 +204,7 @@ Note: Syncfusion usage in the dashboard is already documented above; if a UI for
   - Always compare datetimes in UTC; some DB values may be naive—normalize before comparing (see `routes/events.py`).
   - Scheduler enforces UTC comparisons and normalizes naive timestamps. It publishes only currently active events and clears retained topics for groups with no active events. It also queries a future window (default: 7 days) and expands recurring events using RFC 5545 rules. Event exceptions are respected. Logging is concise and conversion lookups are cached.
 - Use retained MQTT messages for state that clients must recover after reconnect (events per group, client group_id).
-  - Clients should parse `event_type` and then read the corresponding nested payload (`presentation`, `website`, etc.). `website` and `webuntis` use the same nested `website` payload with `type: browser` and a `url`.
+  - Clients should parse `event_type` and then read the corresponding nested payload (`presentation`, `website`, `video`, etc.). `website` and `webuntis` use the same nested `website` payload with `type: browser` and a `url`. Video events include `autoplay`, `loop`, `volume`, and `muted`.
 - In-container DB host is `db`; do not use `localhost` inside services.
 - No separate dev vs prod secret conventions: use the same env var keys across environments (e.g., `DB_CONN`, `MQTT_USER`, `MQTT_PASSWORD`).
 - When adding a new route: