feat: improve scheduler recurrence, DB config, and docs

- Broaden scheduler query window to next N days for proper recurring event expansion (scheduler.py)
- Update DB connection logic for consistent .env loading and fallback (database.py)
- Harden timezone handling and logging in scheduler and DB utils
- Stop auto-deactivating recurring events before recurrence_end (API/events)
- Update documentation to reflect new scheduler, API, and logging behavior

README.md

@@ -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 "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 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.
 - **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**
@@ -160,19 +160,23 @@ For detailed deployment instructions, see:
 - **Database**: MariaDB with timezone-aware timestamps
 - **Features**: RESTful API, file uploads, MQTT integration
    - Recurrence/holidays: returns only master events with `RecurrenceRule` and `RecurrenceException` (EXDATEs) so clients render recurrences and skip holiday instances reliably.
+   - Recurring events are only deactivated after their recurrence_end (UNTIL); non-recurring events deactivate after their end time. Event exceptions are respected and rendered in scheduler output.
    - Single occurrence detach: `POST /api/events/<id>/occurrences/<date>/detach` creates standalone events from recurring series without modifying the master event.
 - **Port**: 8000
 - **Health Check**: `/health`
 
 ### 👂 **Listener** (`listener/`)
-- **Technology**: Python + paho-mqtt
-- **Purpose**: MQTT message processing, client discovery
-- **Features**: Heartbeat monitoring, automatic client registration
 
 ### ⏰ **Scheduler** (`scheduler/`)
-- **Technology**: Python + SQLAlchemy
-- **Purpose**: Event publishing, group-based content distribution
-- **Features**: Time-based event activation, MQTT publishing
+**Technology**: Python + SQLAlchemy
+**Purpose**: Event publishing, group-based content distribution
+**Features**:
+   - Queries a future window (default: 7 days) to expand and publish 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
+   - Logging is concise; conversion lookups are cached and logged only once per media
 
 ### 🔄 **Worker** (Conversion Service)
 - **Technology**: RQ (Redis Queue) + Gotenberg
@@ -345,8 +349,7 @@ mosquitto_sub -h localhost -t "infoscreen/+/heartbeat" -v
 ## 📊 Monitoring & Logging
 
 ### Health Checks
-All services include Docker health checks:
-- API: HTTP endpoint monitoring
+ **Scheduler**: Logging is concise; conversion lookups are cached and logged only once per media.
 - Database: Connection and initialization status
 - MQTT: Pub/sub functionality test
 - Dashboard: Nginx availability