fix(scheduling): enforce one active intervention per current vehicle

Business rule: a running vehicle can hold AT MOST ONE active (sent|executed)
intervention. Switching to a different candidate requires cancelling the
prior one first.

- Server: insertNotification dedup key changes from (suggestion_id,
  candidate_plate) to just suggestion_id; 409 response includes the blocking
  candidate plate
- Detail modal: shows a banner naming the locked candidate; non-active
  candidates render a disabled "该车已有其他干预，请先解除" hint instead
  of the action button
- Batch: pickBestCandidate returns null for any suggestion already holding
  an active intervention — the whole suggestion is excluded

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/server/routes/scheduling/notify.ts

@@ -61,16 +61,20 @@ export async function fetchActiveNotificationMap(): Promise<
 async function insertNotification(
   req: NotifyRequest,
   operator: { id: string | null; name: string | null },
-): Promise<NotificationRecord | { skipped: true }> {
-  // Check if a non-cancelled notification already exists for this pair
+): Promise<NotificationRecord | { skipped: true; existingPlate: string }> {
+  // Business rule: each current vehicle (suggestion) can have AT MOST ONE
+  // active intervention at a time. Any non-cancelled record for the same
+  // suggestion_id blocks further interventions until it is cancelled.
   const [existing] = (await pool.execute(
-    `SELECT id FROM tab_scheduling_notifications
-     WHERE suggestion_id = ? AND candidate_plate = ? AND status != 'cancelled'
+    `SELECT id, candidate_plate FROM tab_scheduling_notifications
+     WHERE suggestion_id = ? AND status != 'cancelled'
      LIMIT 1`,
-    [req.suggestionId, req.candidatePlate],
+    [req.suggestionId],
   )) as [any[], unknown];
 
-  if (existing.length > 0) return { skipped: true };
+  if (existing.length > 0) {
+    return { skipped: true, existingPlate: existing[0].candidate_plate as string };
+  }
 
   const [result] = (await pool.execute(
     `INSERT INTO tab_scheduling_notifications
@@ -110,7 +114,10 @@ app.post('/', async (c) => {
 
     const result = await insertNotification(body, operator);
     if ('skipped' in result) {
-      return c.json({ success: false, message: '该建议已处理' }, 409);
+      return c.json(
+        { success: false, message: `此车已有干预（候选车 ${result.existingPlate}），请先解除` },
+        409,
+      );
     }
 
     console.log(