docs: document flock + cron approach for email agent scheduling

https://claude.ai/code/session_01HaUFs7SaLD5SoiuGCY27Tw

README.md

@@ -1 +1,15 @@
-# Meister-Eder
+# Meister-Eder
+
+## Running the Email Agent
+
+The email agent is a plain script invoked periodically via cron — no long-running daemon needed.
+
+### Scheduling with cron
+
+```cron
+*/5 * * * * flock -n /tmp/meister-eder-email.lock python /path/to/check_email.py
+```
+
+`flock -n` acquires an exclusive lock before running the script. If a previous run is still in progress when the next cron tick fires, the new invocation exits immediately (non-blocking). The lock is released automatically by the kernel when the process ends — even on crash — so stuck locks are not a concern.
+
+Adjust `*/5` to whatever polling interval makes sense (e.g. `*/2` for every 2 minutes).