feedkit: split the former maximumdirect.net/weatherd project in two.

feedkit now contains a reusable core, while weatherfeeder is a concrete implementation that includes weather-specific functions.

scheduler/worker.go

@@ -0,0 +1,7 @@
+package scheduler
+
+// Placeholder for per-source worker logic:
+// - ticker loop
+// - jitter
+// - backoff on errors
+// - emits events into scheduler.Out