Make error messages more descriptive

- Added specific slot time and date to availability error message
- Added appointment ID and context to 'not found' errors
- Added formatted appointment time to past appointment cancellation errors
- Added date context to slot overlap error messages
- All errors now provide actionable information to users

backend/routes/booking.py

@@ -194,7 +194,7 @@ async def create_booking(
     if not matching_availability:
         raise HTTPException(
             status_code=400,
-            detail="Selected slot is not within available time ranges",
+            detail=f"Selected slot at {request.slot_start.strftime('%Y-%m-%d %H:%M')} UTC is not within any available time ranges for {slot_date}. Please select a different time slot.",
         )
     
     # Create the appointment
@@ -264,7 +264,10 @@ async def cancel_my_appointment(
     appointment = result.scalar_one_or_none()
     
     if not appointment:
-        raise HTTPException(status_code=404, detail="Appointment not found")
+        raise HTTPException(
+            status_code=404,
+            detail=f"Appointment with ID {appointment_id} not found. It may have been deleted or the ID is invalid.",
+        )
     
     # Verify ownership
     if appointment.user_id != current_user.id:
@@ -279,9 +282,10 @@ async def cancel_my_appointment(
     
     # Check if appointment is in the past
     if appointment.slot_start <= datetime.now(timezone.utc):
+        appointment_time = appointment.slot_start.strftime('%Y-%m-%d %H:%M') + " UTC"
         raise HTTPException(
             status_code=400,
-            detail="Cannot cancel a past appointment"
+            detail=f"Cannot cancel appointment scheduled for {appointment_time} as it is in the past or has already started."
         )
     
     # Cancel the appointment
@@ -356,7 +360,10 @@ async def admin_cancel_appointment(
     appointment = result.scalar_one_or_none()
     
     if not appointment:
-        raise HTTPException(status_code=404, detail="Appointment not found")
+        raise HTTPException(
+            status_code=404,
+            detail=f"Appointment with ID {appointment_id} not found. It may have been deleted or the ID is invalid.",
+        )
     
     # Check if already cancelled
     if appointment.status != AppointmentStatus.BOOKED:
@@ -367,9 +374,10 @@ async def admin_cancel_appointment(
     
     # Check if appointment is in the past
     if appointment.slot_start <= datetime.now(timezone.utc):
+        appointment_time = appointment.slot_start.strftime('%Y-%m-%d %H:%M') + " UTC"
         raise HTTPException(
             status_code=400,
-            detail="Cannot cancel a past appointment"
+            detail=f"Cannot cancel appointment scheduled for {appointment_time} as it is in the past or has already started."
         )
     
     # Cancel the appointment