feat: Add academic periods system for educational institutions

- Add AcademicPeriod model with support for schuljahr/semester/trimester
- Extend Event and EventMedia models with optional academic_period_id
- Create Alembic migration (8d1df7199cb7) for academic periods system
- Add init script for Austrian school year defaults (2024/25-2026/27)
- Maintain full backward compatibility for existing events/media
- Update program-info.json to version 2025.1.0-alpha.6

Database changes:
- New academic_periods table with unique name constraint
- Foreign key relationships with proper indexing
- Support for multiple period types with single active period

This lays the foundation for period-based organization of events
and media content, specifically designed for school environments
with future extensibility for universities.

models/models.py

@@ -1,5 +1,5 @@
 from sqlalchemy import (
-    Column, Integer, String, Enum, TIMESTAMP, func, Boolean, ForeignKey, Float, Text, Index, DateTime
+    Column, Integer, String, Enum, TIMESTAMP, func, Boolean, ForeignKey, Float, Text, Index, DateTime, Date, UniqueConstraint
 )
 from sqlalchemy.orm import declarative_base, relationship
 import enum
@@ -14,6 +14,12 @@ class UserRole(enum.Enum):
     superadmin = "superadmin"
 
 
+class AcademicPeriodType(enum.Enum):
+    schuljahr = "schuljahr"
+    semester = "semester"
+    trimester = "trimester"
+
+
 class User(Base):
     __tablename__ = 'users'
     id = Column(Integer, primary_key=True, autoincrement=True)
@@ -27,6 +33,42 @@ class User(Base):
     ), onupdate=func.current_timestamp())
 
 
+class AcademicPeriod(Base):
+    __tablename__ = 'academic_periods'
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    name = Column(String(100), nullable=False)  # "Schuljahr 2024/25"
+    display_name = Column(String(50), nullable=True)  # "SJ 24/25" (kurz)
+    start_date = Column(Date, nullable=False, index=True)
+    end_date = Column(Date, nullable=False, index=True)
+    period_type = Column(Enum(AcademicPeriodType),
+                         nullable=False, default=AcademicPeriodType.schuljahr)
+    # nur eine aktive Periode zur Zeit
+    is_active = Column(Boolean, default=False, nullable=False)
+    created_at = Column(TIMESTAMP(timezone=True),
+                        server_default=func.current_timestamp())
+    updated_at = Column(TIMESTAMP(timezone=True), server_default=func.current_timestamp(
+    ), onupdate=func.current_timestamp())
+
+    # Constraint: nur eine aktive Periode zur Zeit
+    __table_args__ = (
+        Index('ix_academic_periods_active', 'is_active'),
+        UniqueConstraint('name', name='uq_academic_periods_name'),
+    )
+
+    def to_dict(self):
+        return {
+            "id": self.id,
+            "name": self.name,
+            "display_name": self.display_name,
+            "start_date": self.start_date.isoformat() if self.start_date else None,
+            "end_date": self.end_date.isoformat() if self.end_date else None,
+            "period_type": self.period_type.value if self.period_type else None,
+            "is_active": self.is_active,
+            "created_at": self.created_at.isoformat() if self.created_at else None,
+            "updated_at": self.updated_at.isoformat() if self.updated_at else None,
+        }
+
+
 class ClientGroup(Base):
     __tablename__ = 'client_groups'
     id = Column(Integer, primary_key=True, autoincrement=True)
@@ -103,6 +145,9 @@ class Event(Base):
     id = Column(Integer, primary_key=True, autoincrement=True)
     group_id = Column(Integer, ForeignKey(
         'client_groups.id'), nullable=False, index=True)
+    academic_period_id = Column(Integer, ForeignKey(
+        # Optional für Rückwärtskompatibilität
+        'academic_periods.id'), nullable=True, index=True)
     title = Column(String(100), nullable=False)
     description = Column(Text, nullable=True)
     start = Column(TIMESTAMP(timezone=True), nullable=False, index=True)
@@ -122,13 +167,18 @@ class Event(Base):
     updated_by = Column(Integer, ForeignKey('users.id'), nullable=True)
     is_active = Column(Boolean, default=True, nullable=False)
 
-    # Add relationship to EventMedia
+    # Add relationships
+    academic_period = relationship(
+        "AcademicPeriod", foreign_keys=[academic_period_id])
     event_media = relationship("EventMedia", foreign_keys=[event_media_id])
 
 
 class EventMedia(Base):
     __tablename__ = 'event_media'
     id = Column(Integer, primary_key=True, autoincrement=True)
+    academic_period_id = Column(Integer, ForeignKey(
+        # Optional für bessere Organisation
+        'academic_periods.id'), nullable=True, index=True)
     media_type = Column(Enum(MediaType), nullable=False)
     url = Column(String(255), nullable=False)
     file_path = Column(String(255), nullable=True)
@@ -136,11 +186,44 @@ class EventMedia(Base):
     uploaded_at = Column(TIMESTAMP, nullable=False,
                          default=lambda: datetime.now(timezone.utc))
 
+    # Add relationship
+    academic_period = relationship(
+        "AcademicPeriod", foreign_keys=[academic_period_id])
+
     def to_dict(self):
         return {
             "id": self.id,
+            "academic_period_id": self.academic_period_id,
             "media_type": self.media_type.value if self.media_type else None,
             "url": self.url,
             "file_path": self.file_path,
             "message_content": self.message_content,
         }
+
+
+class SchoolHoliday(Base):
+    __tablename__ = 'school_holidays'
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    name = Column(String(150), nullable=False)
+    start_date = Column(Date, nullable=False, index=True)
+    end_date = Column(Date, nullable=False, index=True)
+    region = Column(String(100), nullable=True, index=True)
+    source_file_name = Column(String(255), nullable=True)
+    imported_at = Column(TIMESTAMP(timezone=True),
+                         server_default=func.current_timestamp())
+
+    __table_args__ = (
+        UniqueConstraint('name', 'start_date', 'end_date',
+                         'region', name='uq_school_holidays_unique'),
+    )
+
+    def to_dict(self):
+        return {
+            "id": self.id,
+            "name": self.name,
+            "start_date": self.start_date.isoformat() if self.start_date else None,
+            "end_date": self.end_date.isoformat() if self.end_date else None,
+            "region": self.region,
+            "source_file_name": self.source_file_name,
+            "imported_at": self.imported_at.isoformat() if self.imported_at else None,
+        }