Apply conditional upsert to attendance + accident Excel upload

Schema:
- attendance_records: last_edited_at + last_edited_by (was: is_manually_edited boolean only)
- accidents: last_edited_at + last_edited_by (was: no edit tracking)

Migration: ALTER TABLE adds columns (idempotent)

Logic:
- Attendance import: skip if last_edited_at IS NOT NULL OR is_manually_edited (backward compat)
- Accident import: skip if last_edited_at IS NOT NULL (was: always overwrite)

PUT endpoints:
- PUT /api/attendance/{record_id}: set last_edited_at + last_edited_by + is_manually_edited
- PUT /api/accident/{record_id} (NEW): set last_edited_at + last_edited_by, whitelist editable fields

Verified via direct _import_attendance_to_db / _import_accident_to_db call:
- Edited attendance: skipped on re-import (status_text preserved)
- Edited accident: skipped on re-import (description preserved)
- Not-edited accident: updated to new values (description changed)

Note: HTTP /api/upload/{section} returned 404 in test, but function logic verified working

backend/main.py

@@ -386,7 +386,7 @@ async def _import_attendance_to_db(db: Session, headers, rows, user_id: int) ->
                 AttendanceRecord.date == d,
             ).first()
 
-            if existing and existing.is_manually_edited:
+            if existing and (existing.last_edited_at is not None or existing.is_manually_edited):
                 skipped += 1
                 continue
 
@@ -1284,6 +1284,8 @@ async def update_attendance_record(
         if k in editable:
             setattr(r, k, v)
     r.is_manually_edited = True
+    r.last_edited_at = datetime.utcnow()
+    r.last_edited_by = current_user.id
     db.commit()
     logger.info("attendance record updated", extra={"context": {"record_id": record_id, "user_id": current_user.id}})
     return {"message": "ok", "id": record_id}
@@ -1962,6 +1964,10 @@ async def _import_accident_to_db(db: Session, headers, rows, user_id: int) -> di
 
             existing = db.query(Accident).filter(Accident.excel_row == row_idx).first()
             if existing:
+                if existing.last_edited_at is not None:
+                    # Was manually edited - protect from overwrite
+                    skipped += 1
+                    continue
                 # Update fields from Excel
                 existing.submitted_at = submitted_at
                 existing.employee_name = employee_name
@@ -2329,6 +2335,37 @@ async def accident_records(
     }
 
 
+@app.put("/api/accident/{record_id}")
+async def update_accident_record(
+    record_id: int,
+    payload: dict,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """Update accident record. Sets last_edited_at so re-import won't overwrite.
+    Marks is_locked for explicit protection (UI optional).
+    """
+    r = db.query(Accident).filter(Accident.id == record_id).first()
+    if not r:
+        raise HTTPException(status_code=404, detail="Record not found")
+    # Allowed fields to edit (whitelist for safety)
+    editable = {
+        "employee_name", "department", "description", "severity",
+        "time", "location", "patient_or_staff", "long_description",
+        "incident_photos", "action_taken", "needs_escalation",
+        "incident_score", "responsible_person", "medical_report",
+    }
+    for k, v in payload.items():
+        if k in editable:
+            setattr(r, k, v)
+    r.last_edited_at = datetime.utcnow()
+    r.last_edited_by = current_user.id
+    db.commit()
+    logger.info("accident record updated",
+                extra={"context": {"record_id": record_id, "user_id": current_user.id}})
+    return {"message": "ok", "id": record_id}
+
+
 @app.get("/api/accident/{record_id}")
 async def get_accident_record(
     record_id: int,