feat(cis): implement /database/timetables/current-period endpoint with Neo4j query

- Query Neo4j for Academic/Registration periods where now() is between start_time and end_time
- Return period_id, event_type, event_label, start_time, end_time
- Handles missing teacher or Neo4j connection gracefully

routers/database/init/timetables.py

@@ -162,13 +162,84 @@ async def process_worker_timetable(file_content, user_node_data, worker_node_dat
     finally:
         logging.info(f"Closing driver for {worker_node_data['worker_db_name']}")
         driver.close_driver(neo_driver)
+
 @router.get("/current-period")
 async def get_current_period(user_id: str = ""):
-    # Phase 1: return stub — TODO: implement Neo4j query in Phase 2
-    return {
-        "period_id": None,
-        "event_type": None,
-        "event_label": None,
-        "start_time": None,
-        "end_time": None,
-    }
+    """Get the current active timetable period for a teacher.
+    
+    Queries Neo4j for Academic or Registration periods where now() falls
+    between start_time and end_time for the given teacher's uuid_string.
+    """
+    if not user_id:
+        return {
+            "period_id": None,
+            "event_type": None,
+            "event_label": None,
+            "start_time": None,
+            "end_time": None,
+        }
+    
+    # The user_id from Supabase JWT maps to the TeacherNode's uuid_string
+    teacher_uuid = user_id
+    
+    # Try to find the current period across all known databases
+    # First, try to get the user's database name from the UserNode
+    neo_driver = driver.get_driver()
+    if neo_driver is None:
+        logging.error("Failed to connect to Neo4j for current-period query")
+        return {
+            "period_id": None,
+            "event_type": None,
+            "event_label": None,
+            "start_time": None,
+            "end_time": None,
+        }
+    
+    try:
+        # Query for the current period
+        # Look for Teacher nodes with matching uuid_string that have relationships to Academic/Registration periods
+        query = """
+        MATCH (t:Teacher {uuid_string: $teacher_uuid})-[:HAS_PERIOD]->(p:AcademicPeriod|RegistrationPeriod)
+        WHERE p.start_time <= datetime() AND p.end_time >= datetime()
+        RETURN p.uuid_string AS period_id,
+               p.name AS event_label,
+               p.start_time AS start_time,
+               p.end_time AS end_time,
+               CASE WHEN p:AcademicPeriod THEN 'lesson' ELSE 'registration' END AS event_type
+        ORDER BY p.start_time ASC
+        LIMIT 1
+        """
+        
+        with neo_driver.session() as session:
+            result = session.run(query, teacher_uuid=teacher_uuid)
+            record = result.single()
+            
+            if record:
+                logging.info(f"Found current period for teacher {teacher_uuid}: {record['event_label']}")
+                return {
+                    "period_id": record["period_id"],
+                    "event_type": record["event_type"],
+                    "event_label": record["event_label"],
+                    "start_time": str(record["start_time"]) if record["start_time"] else None,
+                    "end_time": str(record["end_time"]) if record["end_time"] else None,
+                }
+            else:
+                logging.info(f"No current period found for teacher {teacher_uuid}")
+                return {
+                    "period_id": None,
+                    "event_type": None,
+                    "event_label": None,
+                    "start_time": None,
+                    "end_time": None,
+                }
+    except Exception as e:
+        logging.error(f"Error querying current period: {str(e)}")
+        return {
+            "period_id": None,
+            "event_type": None,
+            "event_label": None,
+            "start_time": None,
+            "end_time": None,
+        }
+    finally:
+        driver.close_driver(neo_driver)