feat: define all 8 SQLModel tables

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/models/workout_session.py

@@ -0,0 +1,31 @@
+"""WorkoutSession model for tracking completed workout sessions.
+
+Each session ties a user to a workout day on a specific date.
+"""
+
+import datetime as dt
+from typing import Optional
+
+from sqlmodel import Field, SQLModel
+
+
+class WorkoutSession(SQLModel, table=True):
+    """A completed workout session.
+
+    Attributes:
+        id: Primary key, auto-incremented.
+        user_id: FK to users table.
+        workout_day_id: FK to workout_days table.
+        date: The date the workout was performed.
+        notes: Optional free-text notes about the session.
+        created_at: Timestamp when the record was created.
+    """
+
+    __tablename__ = "workout_sessions"
+
+    id: Optional[int] = Field(default=None, primary_key=True)
+    user_id: int = Field(foreign_key="users.id", index=True)
+    workout_day_id: int = Field(foreign_key="workout_days.id")
+    date: dt.date = Field(default_factory=dt.date.today)
+    notes: Optional[str] = Field(default=None)
+    created_at: dt.datetime = Field(default_factory=dt.datetime.utcnow)