fix: resolve template errors, orphaned sessions, and auth redirects

- Fix exercise_id undefined error in log_form.html by using scalar
  exercise_id instead of exercise.id object reference
- Clean up orphaned WorkoutSession records when all logs are deleted
- Filter empty sessions from dashboard stats (sessions, volume, streak)
- Replace broken HTTPException auth redirect with custom exception
  handler that properly returns 302 to /login

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

app/services/analytics_service.py

@@ -48,23 +48,28 @@ class AnalyticsService:
             Dict with keys: total_sessions, total_volume, total_sets,
             current_streak, last_workout_date.
         """
-        sessions = self._session.exec(
+        all_sessions = self._session.exec(
             select(WorkoutSession)
             .where(WorkoutSession.user_id == user_id)
             .order_by(WorkoutSession.date.desc())
         ).all()
-        total_sessions = len(sessions)
 
+        # Only count sessions that still have log entries
+        sessions = []
         total_volume = 0.0
         total_sets = 0
-        for ws in sessions:
+        for ws in all_sessions:
             logs = self._session.exec(
                 select(WorkoutLog).where(WorkoutLog.session_id == ws.id)
             ).all()
+            if not logs:
+                continue
+            sessions.append(ws)
             for log_entry in logs:
                 total_sets += 1
                 weight = _weight_to_float(log_entry.weight_used)
                 total_volume += log_entry.reps_completed * weight
+        total_sessions = len(sessions)
 
         current_streak = 0
         if sessions:
@@ -162,6 +167,9 @@ class AnalyticsService:
                 select(WorkoutLog).where(WorkoutLog.session_id == ws.id)
             ).all()
 
+            if not logs:
+                continue
+
             day_volume = sum(
                 log_entry.reps_completed * _weight_to_float(log_entry.weight_used)
                 for log_entry in logs

app/services/log_service.py

@@ -149,6 +149,8 @@ class LogService:
     def delete_log(self, log_id: int) -> None:
         """Delete a log entry.
 
+        Removes the log and cleans up the parent session if no logs remain.
+
         Args:
             log_id: The log entry ID.
 
@@ -159,10 +161,22 @@ class LogService:
         if log is None:
             raise ValueError(f"WorkoutLog with id {log_id} not found")
 
+        session_id = log.session_id
         self._session.delete(log)
         self._session.commit()
         logger.info("log_deleted", log_id=log_id)
 
+        # Clean up orphaned session if no logs remain
+        remaining = self._session.exec(
+            select(WorkoutLog).where(WorkoutLog.session_id == session_id)
+        ).first()
+        if remaining is None:
+            ws = self._session.get(WorkoutSession, session_id)
+            if ws:
+                self._session.delete(ws)
+                self._session.commit()
+                logger.info("session_deleted_empty", session_id=session_id)
+
     def get_latest_logs_for_exercise(
         self,
         user_id: int,