feat(academic-periods): period selector, active period

API, holiday indicators; UI polish; bump version

Dashboard:

Add Syncfusion academic period dropdown next to group selector
Navigate scheduler to today's month/day within selected period year on change
Show adjacent holiday plan badge; keep "holidays in view" counter on the right
Compact dropdown widths for a tighter toolbar
Default blocking of scheduling on holidays; block entries styled like all-day; black text styling
API:

Add academic periods routes: list, get active, set active (POST), for_date
Register blueprint in wsgi
Holidays:

Support TXT/CSV upload; headerless TXT uses columns 2-4; region remains null
Docs:

Update shared Copilot instructions with academic periods endpoints and dashboard integration details

.github/copilot-instructions.md

@@ -24,8 +24,9 @@ Use this as your shared context when proposing changes. Keep edits minimal and m
 - Screenshots: server-side folders `server/received_screenshots/` and `server/screenshots/`; Nginx exposes `/screenshots/{uuid}.jpg` via `server/wsgi.py` route.
 
 ## Data model highlights (see `models/models.py`)
-- Enums: `EventType` (presentation, website, video, message, webuntis) and `MediaType` (file/website types).
-- Tables: `clients`, `client_groups`, `events`, `event_media`, `users`.
+- Enums: `EventType` (presentation, website, video, message, webuntis), `MediaType` (file/website types), and `AcademicPeriodType` (schuljahr, semester, trimester).
+- Tables: `clients`, `client_groups`, `events`, `event_media`, `users`, `academic_periods`, `school_holidays`.
+- Academic periods: `academic_periods` table supports educational institution cycles (school years, semesters). Events and media can be optionally linked via `academic_period_id` (nullable for backward compatibility).
 - Times are stored as timezone-aware; treat comparisons in UTC (see scheduler and routes/events).
 
 ## API patterns
@@ -36,11 +37,19 @@ Use this as your shared context when proposing changes. Keep edits minimal and m
   - Groups: `server/routes/groups.py` computes “alive” using a grace period that varies by `ENV`.
   - Events: `server/routes/events.py` serializes enum values to strings and normalizes times to UTC.
   - Media: `server/routes/eventmedia.py` implements a simple file manager API rooted at `server/media/`.
+  - Academic periods: `server/routes/academic_periods.py` exposes:
+    - `GET /api/academic_periods` — list all periods
+    - `GET /api/academic_periods/active` — currently active period
+    - `POST /api/academic_periods/active` — set active period (deactivates others)
+    - `GET /api/academic_periods/for_date?date=YYYY-MM-DD` — period covering given date
 
 ## Frontend patterns (dashboard)
 - Vite React app; proxies `/api` and `/screenshots` to API in dev (`vite.config.ts`).
 - Uses Syncfusion components; Vite config pre-bundles specific packages to avoid alias issues.
 - Environment: `VITE_API_URL` provided at build/run; in dev compose, proxy handles `/api` so local fetches can use relative `/api/...` paths.
+ - Scheduler (appointments page): top bar includes Group and Academic Period selectors (Syncfusion DropDownList). Selecting a period calls `POST /api/academic_periods/active`, moves the calendar to today’s month/day within the period year, and refreshes a right-aligned indicator row showing:
+   - Holidays present in the current view (count)
+   - Period label (display_name or name) with a badge indicating whether any holidays exist in that period (overlap check)
 
 ## Local development
 - Compose: development is `docker-compose.yml` + `docker-compose.override.yml`.
@@ -49,6 +58,7 @@ Use this as your shared context when proposing changes. Keep edits minimal and m
   - Mosquitto: allows anonymous in dev; WebSocket on :9001.
 - Common env vars: `DB_CONN`, `DB_USER`, `DB_PASSWORD`, `DB_HOST=db`, `DB_NAME`, `ENV`, `MQTT_USER`, `MQTT_PASSWORD`.
 - Alembic: prod compose runs `alembic ... upgrade head` and `server/init_defaults.py` before gunicorn.
+  - Use `server/init_academic_periods.py` to populate default Austrian school years after migration.
 
 ## Production
 - `docker-compose.prod.yml` uses prebuilt images (`ghcr.io/robbstarkaustria/*`).
@@ -74,6 +84,7 @@ Use this as your shared context when proposing changes. Keep edits minimal and m
   3) Manage `Session()` lifecycle, and
   4) Return JSON-safe values (serialize enums and datetimes).
 - When extending media types, update `MediaType` and any logic in `eventmedia` and dashboard that depends on it.
+- Academic periods: Events/media can be optionally associated with periods for educational organization. Only one period should be active at a time (`is_active=True`).
 
 ## Quick examples
 - Add client description persists to DB and publishes group via MQTT: see `PUT /api/clients/<uuid>/description` in `routes/clients.py`.
@@ -81,3 +92,10 @@ Use this as your shared context when proposing changes. Keep edits minimal and m
 - Listener heartbeat path: `infoscreen/<uuid>/heartbeat` → sets `clients.last_alive`.
 
 Questions or unclear areas? Tell us if you need: exact devcontainer debugging steps, stricter Alembic workflow, or a seed dataset beyond `init_defaults.py`.
+
+## Academic Periods System
+- **Purpose**: Organize events and media by educational cycles (school years, semesters, trimesters).
+- **Design**: Fully backward compatible - existing events/media continue to work without period assignment.
+- **Usage**: New events/media can optionally reference `academic_period_id` for better organization and filtering.
+- **Constraints**: Only one period can be active at a time; use `init_academic_periods.py` for Austrian school year setup.
+ - **UI Integration**: The dashboard highlights the currently selected period and whether a holiday plan exists within that date range. Holiday linkage currently uses date overlap with `school_holidays`; an explicit `academic_period_id` on `school_holidays` can be added later if tighter association is required.