feat: presentation defaults + scheduler active-only

Add Settings → Events (Presentations) defaults (interval, page-progress,
auto-progress) persisted via /api/system-settings
Seed defaults in init_defaults.py (10/true/true)
Add Event.page_progress and Event.auto_progress (Alembic applied)
CustomEventModal applies defaults on create and saves fields
Scheduler publishes only currently active events per group, clears retained
topics when none, normalizes times to UTC; include flags in payloads
Docs: update README, copilot instructions, and DEV-CHANGELOG
If you can split the commit, even better

feat(dashboard): add presentation defaults UI
feat(api): seed presentation defaults in init_defaults.py
feat(model): add Event.page_progress and Event.auto_progress
feat(scheduler): publish only active events; clear retained topics; UTC
docs: update README and copilot-instructions
chore: update DEV-CHANGELOG

README.md

@@ -39,7 +39,7 @@ A comprehensive multi-service digital signage solution for educational instituti
 
 Data flow summary:
 - Listener: consumes discovery and heartbeat messages from the MQTT Broker and updates the API Server (client registration/heartbeats).
-- Scheduler: reads events from the API Server and publishes active content to the MQTT Broker (retained topics per group) for clients.
+- Scheduler: reads events from the API Server and publishes only currently active content to the MQTT Broker (retained topics per group). When a group has no active events, the scheduler clears its retained topic by publishing an empty list. All time comparisons are done in UTC; any naive timestamps are normalized.
 - Clients: send discovery/heartbeat via the MQTT Broker (handled by the Listener) and receive content from the Scheduler via MQTT.
 - Worker: receives conversion commands directly from the API Server and reports results/status back to the API (no MQTT involved).
 - MariaDB: is accessed exclusively by the API Server. The Dashboard never talks to the database directly; it only communicates with the API.
@@ -66,7 +66,7 @@ Data flow summary:
 - **Videos**: Media file streaming
 - **Messages**: Text announcements
 - **WebUntis**: Educational schedule integration
- - **Recurrence & Holidays**: Recurring events can be configured to skip holidays. The backend generates EXDATEs (RecurrenceException) for holiday occurrences using RFC 5545 timestamps (yyyyMMddTHHmmssZ), so the calendar never shows those instances. The scheduler expands recurring events for the next 7 days, applies event exceptions, and only deactivates recurring events after their recurrence_end (UNTIL). The "Termine an Ferientagen erlauben" toggle does not affect these events.
+ - **Recurrence & Holidays**: Recurring events can be configured to skip holidays. The backend generates EXDATEs (RecurrenceException) for holiday occurrences using RFC 5545 timestamps (yyyyMMddTHHmmssZ), so the calendar never shows those instances. The scheduler queries a 7-day window to expand recurring events and applies event exceptions, but only publishes events that are active at the current time (UTC). The "Termine an Ferientagen erlauben" toggle does not affect these events.
 - **Single Occurrence Editing**: Users can edit individual occurrences of recurring events without affecting the master series. The system provides a confirmation dialog to choose between editing a single occurrence or the entire series.
 
 ### 🏫 **Academic Period Management**
@@ -171,11 +171,13 @@ For detailed deployment instructions, see:
 **Technology**: Python + SQLAlchemy
 **Purpose**: Event publishing, group-based content distribution
 **Features**:
-   - Queries a future window (default: 7 days) to expand and publish recurring events
+   - Queries a future window (default: 7 days) to expand recurring events
    - Expands recurrences using RFC 5545 rules
    - Applies event exceptions (skipped dates, detached occurrences)
    - Only deactivates recurring events after their recurrence_end (UNTIL)
-   - Publishes all valid occurrences to MQTT
+   - Publishes only currently active events to MQTT (per group)
+   - Clears retained topics by publishing an empty list when a group has no active events
+   - Normalizes naive timestamps and compares times in UTC
    - Logging is concise; conversion lookups are cached and logged only once per media
 
 ### 🔄 **Worker** (Conversion Service)
@@ -297,6 +299,10 @@ mosquitto_sub -h localhost -t "infoscreen/+/heartbeat" -v
 - `DELETE /api/system-settings/{key}` - Delete a setting (admin+)
 - `GET /api/system-settings/supplement-table` - Get WebUntis/Vertretungsplan settings (enabled, url)
 - `POST /api/system-settings/supplement-table` - Update WebUntis/Vertretungsplan settings
+   - Presentation defaults stored as keys:
+      - `presentation_interval` (seconds, default "10")
+      - `presentation_page_progress` ("true"/"false", default "true")
+      - `presentation_auto_progress` ("true"/"false", default "true")
 
 ### Health & Monitoring
 - `GET /health` - Service health check
@@ -332,7 +338,7 @@ mosquitto_sub -h localhost -t "infoscreen/+/heartbeat" -v
    - 📅 Academic Calendar (all users): School Holidays import/list and Academic Periods (set active period)
    - 🖥️ Display & Clients (admin+): Defaults placeholders and quick links to Clients/Groups
    - 🎬 Media & Files (admin+): Upload settings placeholders and Conversion status overview
-   - 🗓️ Events (admin+): WebUntis/Vertretungsplan URL enable/disable, save, preview; placeholders for other event types
+   - 🗓️ Events (admin+): WebUntis/Vertretungsplan URL enable/disable, save, preview. Presentations: general defaults for slideshow interval, page-progress, and auto-progress; persisted via `/api/system-settings` keys and applied on create in the event modal.
    - ⚙️ System (superadmin): Organization info and Advanced configuration placeholders
 - **Holidays**: Academic calendar management
  - **Program info**: Version, build info, tech stack and paginated changelog (reads `dashboard/public/program-info.json`)