BE-CAL-001: Add TimeSlot model with SlotType/SlotStatus/EventType enums

- New calendar.py model file with TimeSlot table definition
- SlotType enum: work, on_call, entertainment, system
- SlotStatus enum: not_started, ongoing, deferred, skipped, paused, finished, aborted
- EventType enum: job, entertainment, system_event
- All fields per design doc: user_id, date, slot_type, estimated_duration,
  scheduled_at, started_at, attended, actual_duration, event_type, event_data (JSON),
  priority, status, plan_id (FK to schedule_plans)

app/models/calendar.py

@@ -0,0 +1,143 @@
+"""Calendar models — TimeSlot and related enums.
+
+TimeSlot represents a single scheduled slot on a user's calendar.
+Slots can be created manually or materialized from a SchedulePlan.
+
+See: NEXT_WAVE_DEV_DIRECTION.md §1.1
+"""
+
+from sqlalchemy import (
+    Column, Integer, String, Text, DateTime, Date, Time,
+    ForeignKey, Enum, Boolean, JSON,
+)
+from sqlalchemy.sql import func
+from app.core.config import Base
+import enum
+
+
+# ---------------------------------------------------------------------------
+# Enums
+# ---------------------------------------------------------------------------
+
+class SlotType(str, enum.Enum):
+    """What kind of slot this is."""
+    WORK = "work"
+    ON_CALL = "on_call"
+    ENTERTAINMENT = "entertainment"
+    SYSTEM = "system"
+
+
+class SlotStatus(str, enum.Enum):
+    """Lifecycle status of a slot."""
+    NOT_STARTED = "not_started"
+    ONGOING = "ongoing"
+    DEFERRED = "deferred"
+    SKIPPED = "skipped"
+    PAUSED = "paused"
+    FINISHED = "finished"
+    ABORTED = "aborted"
+
+
+class EventType(str, enum.Enum):
+    """High-level event category stored alongside the slot."""
+    JOB = "job"
+    ENTERTAINMENT = "entertainment"
+    SYSTEM_EVENT = "system_event"
+
+
+# ---------------------------------------------------------------------------
+# TimeSlot model
+# ---------------------------------------------------------------------------
+
+class TimeSlot(Base):
+    __tablename__ = "time_slots"
+
+    id = Column(Integer, primary_key=True, index=True)
+
+    user_id = Column(
+        Integer,
+        ForeignKey("users.id"),
+        nullable=False,
+        index=True,
+        comment="Owner of this slot",
+    )
+
+    date = Column(
+        Date,
+        nullable=False,
+        index=True,
+        comment="Calendar date for this slot",
+    )
+
+    slot_type = Column(
+        Enum(SlotType, values_callable=lambda x: [e.value for e in x]),
+        nullable=False,
+        comment="work | on_call | entertainment | system",
+    )
+
+    estimated_duration = Column(
+        Integer,
+        nullable=False,
+        comment="Estimated duration in minutes (1-50)",
+    )
+
+    scheduled_at = Column(
+        Time,
+        nullable=False,
+        comment="Planned start time (00:00-23:00)",
+    )
+
+    started_at = Column(
+        Time,
+        nullable=True,
+        comment="Actual start time (filled when slot begins)",
+    )
+
+    attended = Column(
+        Boolean,
+        default=False,
+        nullable=False,
+        comment="Whether the slot has been attended",
+    )
+
+    actual_duration = Column(
+        Integer,
+        nullable=True,
+        comment="Actual duration in minutes (0-65535), no upper design limit",
+    )
+
+    event_type = Column(
+        Enum(EventType, values_callable=lambda x: [e.value for e in x]),
+        nullable=True,
+        comment="job | entertainment | system_event",
+    )
+
+    event_data = Column(
+        JSON,
+        nullable=True,
+        comment="Event details JSON — structure depends on event_type",
+    )
+
+    priority = Column(
+        Integer,
+        nullable=False,
+        default=0,
+        comment="Priority 0-99, higher = more important",
+    )
+
+    status = Column(
+        Enum(SlotStatus, values_callable=lambda x: [e.value for e in x]),
+        nullable=False,
+        default=SlotStatus.NOT_STARTED,
+        comment="Lifecycle status of this slot",
+    )
+
+    plan_id = Column(
+        Integer,
+        ForeignKey("schedule_plans.id"),
+        nullable=True,
+        comment="Source plan if materialized from a SchedulePlan; set NULL on edit/cancel",
+    )
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())