feat: add smart "Workout Now" recommendation to workout picker

Auto-recommends the next workout in the 4-day cycle based on the
user's last completed session (one with logged sets). Redesigns
the /workouts page with highlighted recommendation card and
renames the back button to "Change Workout".

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

app/routes/workouts.py

@@ -14,6 +14,7 @@ from sqlmodel import Session, select
 from app.database import get_db_session
 from app.models.user import User
 from app.models.user_exercise_program import UserExerciseProgram
+from app.models.workout_day import WorkoutDay
 from app.services.exercise_service import ExerciseService
 from app.services.log_service import LogService
 from app.services.progression_service import ProgressionService
@@ -31,14 +32,40 @@ async def workout_days_list(
     session: Session = Depends(get_db_session),
     profile: User = Depends(require_active_profile),
 ):
-    """List all workout days as clickable cards."""
+    """List all workout days with a recommendation for what to do next."""
     exercise_service = ExerciseService(session)
     days = exercise_service.list_workout_days()
 
+    ws_service = WorkoutSessionService(session)
+    last_session = ws_service.get_last_completed_session(profile.id)
+
+    recommended_day_id = None
+    last_workout_name = None
+    last_workout_date = None
+
+    if last_session:
+        last_day = session.get(WorkoutDay, last_session.workout_day_id)
+        if last_day:
+            last_workout_name = last_day.name
+            last_workout_date = last_session.date
+            next_day_number = (last_day.day_number % 4) + 1
+            for d in days:
+                if d.day_number == next_day_number:
+                    recommended_day_id = d.id
+                    break
+    else:
+        for d in days:
+            if d.day_number == 1:
+                recommended_day_id = d.id
+                break
+
     templates = request.app.state.templates
     return templates.TemplateResponse("pages/workout_days.html", {
         "request": request,
         "days": days,
+        "recommended_day_id": recommended_day_id,
+        "last_workout_name": last_workout_name,
+        "last_workout_date": last_workout_date,
     })