feat(matching): implement origin_run_id tracking and audit tests

- Updated run-matching endpoint to create MatchingRun records
- Added trigger tracking (manual vs scheduler)
- Fixed saveMatchingResults to accept runId parameter
- Added comprehensive audit tests (matching-runs-audit.test.js):
  * TC1: origin_run_id assigned correctly
  * TC2: Sequential runs create separate run IDs
  * TC3: Accepted suggestions preserve origin_run_id
  * TC4: Filter parameters (onlyAssigned, includeNotFound)
  * TC5: Manual vs scheduler trigger differentiation
  * TC6: Failed runs recorded in audit trail
- All 6 audit tests passing

backend/src/routes/events.js

@@ -1144,25 +1144,65 @@ router.post('/:slug/run-matching', authenticate, async (req, res, next) => {
     // TODO: In production, add admin check or deadline validation
     // For now, allow anyone to run matching for testing
 
-    // Run matching algorithm
-    const suggestions = await matchingService.runMatching(event.id);
+    const startedAt = new Date();
+    let runRow = null;
 
-    // Save results
-    const count = await matchingService.saveMatchingResults(event.id, suggestions);
+    try {
+      // Create run audit row
+      runRow = await prisma.matchingRun.create({
+        data: {
+          eventId: event.id,
+          trigger: 'manual',
+          status: 'running',
+          startedAt,
+        },
+      });
 
-    // Get statistics
-    const notFoundCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.NOT_FOUND).length;
-    const matchedCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.PENDING).length;
+      // Run matching algorithm
+      const suggestions = await matchingService.runMatching(event.id);
 
-    res.json({
-      success: true,
-      data: {
-        totalHeats: suggestions.length,
-        matched: matchedCount,
-        notFound: notFoundCount,
-        runAt: new Date(),
-      },
-    });
+      // Save results with runId for audit trail
+      const count = await matchingService.saveMatchingResults(event.id, suggestions, runRow.id);
+
+      // Get statistics
+      const notFoundCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.NOT_FOUND).length;
+      const matchedCount = suggestions.filter(s => s.status === SUGGESTION_STATUS.PENDING).length;
+
+      // Update run audit row with success
+      await prisma.matchingRun.update({
+        where: { id: runRow.id },
+        data: {
+          status: 'success',
+          endedAt: new Date(),
+          matchedCount,
+          notFoundCount,
+        },
+      });
+
+      res.json({
+        success: true,
+        data: {
+          totalHeats: suggestions.length,
+          matched: matchedCount,
+          notFound: notFoundCount,
+          runAt: new Date(),
+          runId: runRow.id,
+        },
+      });
+    } catch (error) {
+      // Update run audit row with failure
+      if (runRow) {
+        await prisma.matchingRun.update({
+          where: { id: runRow.id },
+          data: {
+            status: 'failed',
+            endedAt: new Date(),
+            errorMessage: error.message,
+          },
+        });
+      }
+      throw error;
+    }
   } catch (error) {
     next(error);
   }