chore: allow manual nightly-tests pipeline run

docs/test-slow-suite.md

@@ -134,6 +134,26 @@ just test-all --max-failures 5
 - Executes daily at 2 AM via cron trigger
 - Pipeline name: `nightly-tests`
 
+**Manual Execution:**
+
+The nightly pipeline can be manually triggered using:
+
+**Drone CLI:**
+```bash
+drone build start <owner>/<repo> <branch> --event custom
+```
+
+**Drone Web UI:**
+- Navigate to the repository in Drone
+- Go to the `nightly-tests` pipeline
+- Click "Run" or "Restart" and select event type `custom`
+
+**Example:**
+```bash
+# Trigger nightly-tests pipeline manually
+drone build start local-it/mitgliederverwaltung main --event custom
+```
+
 ---
 
 ## Best Practices for New Performance Tests