fix(sensor-placement): enforce project write boundaries

Bind every scheme request to ProjectContext, keep viewer access read-only, reject concurrent optimization jobs without blocking worker threads, and cap export/update payload sizes. Run optimization and workbook work off the event loop.

app/algorithms/sensor/__init__.py

@@ -7,6 +7,7 @@ from app.algorithms.sensor import kmeans as kmeans_sensor
 from app.algorithms.sensor import sensitivity
 from app.native.wndb.s42_sensor_placement import create_sensor_placement
 from app.services.sensor_placement import (
+    SensorPlacementConflictError,
     SensorPlacementValidationError,
     validate_sensor_placement_nodes,
 )
@@ -31,7 +32,15 @@ def _sensor_inp_lock(name: str):
     inp_path.parent.mkdir(parents=True, exist_ok=True)
     lock_path = inp_path.with_suffix(".sensor.lock")
     with lock_path.open("w", encoding="utf-8") as lock_file:
-        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
+        try:
+            fcntl.flock(
+                lock_file.fileno(),
+                fcntl.LOCK_EX | fcntl.LOCK_NB,
+            )
+        except BlockingIOError as exc:
+            raise SensorPlacementConflictError(
+                "当前项目已有监测点优化任务正在运行，请稍后重试"
+            ) from exc
         try:
             yield inp_path
         finally: