Flatten to a single package directory

The checkout is now astrape/astrape-ems, not astrape/astrape-ems/<package>. The package
contents move to the repository root and pyproject maps the package name to
'.' via package-dir, with the subpackages listed explicitly.

The systemd units move out to /srv/astrape/deploy/systemd, outside every
repository, because they describe this deployment rather than any one
component.

Verified both install modes: editable, which is how the deployment runs, and
a plain wheel install, which is what the container build does.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/daemons/plant_daemon.py

@@ -0,0 +1,95 @@
+from __future__ import annotations
+
+import argparse
+from dataclasses import dataclass
+from os import environ
+from sys import stderr
+from time import sleep
+
+from astrape_ems.classes.env import EnvLoader
+from astrape_ems.classes.client import SigenPlantClient
+from astrape_ems.classes.store import SigenStore
+
+
+@dataclass(frozen=True)
+class SigenDaemonConfig:
+    poll_seconds: float
+
+    @classmethod
+    def from_env(cls) -> "SigenDaemonConfig":
+        return cls(
+            poll_seconds=float(environ.get("SIGEN_POLL_SECONDS", "5")),
+        )
+
+
+class SigenDaemon:
+    """Polls Sigenergy plant metrics and stores normalized snapshots."""
+
+    def __init__(
+        self,
+        config: SigenDaemonConfig,
+        plant_client: SigenPlantClient,
+        sigen_store: SigenStore,
+    ) -> None:
+        self.config = config
+        self.plant_client = plant_client
+        self.sigen_store = sigen_store
+
+    @classmethod
+    def from_env(cls) -> "SigenDaemon":
+        return cls(
+            config=SigenDaemonConfig.from_env(),
+            plant_client=SigenPlantClient.from_env(),
+            sigen_store=SigenStore.from_env(),
+        )
+
+    def initialize(self) -> None:
+        self.sigen_store.initialize()
+
+    def run_once(self) -> int:
+        snapshot = self.plant_client.fetch_snapshot()
+        return self.sigen_store.save_snapshot(snapshot)
+
+    def run_forever(self) -> None:
+        self.initialize()
+        while True:
+            try:
+                saved_count = self.run_once()
+                print(f"stored_sigen_plant_snapshots={saved_count}", flush=True)
+            except Exception as error:
+                print(f"sigen_poll_error={error}", file=stderr, flush=True)
+
+            sleep(self.config.poll_seconds)
+
+
+def main() -> None:
+    try:
+        EnvLoader().load()
+        daemon = SigenDaemon.from_env()
+        args = parse_args()
+        if args.once:
+            daemon.initialize()
+            saved_count = daemon.run_once()
+            print(f"stored_sigen_plant_snapshots={saved_count}", flush=True)
+            return
+
+        daemon.run_forever()
+    except Exception as error:
+        print(f"sigen_daemon_startup_error={error}", file=stderr)
+        raise SystemExit(1) from error
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(
+        description="Poll Sigenergy plant metrics into Astrape's database."
+    )
+    parser.add_argument(
+        "--once",
+        action="store_true",
+        help="Initialize storage, save one snapshot, and exit.",
+    )
+    return parser.parse_args()
+
+
+if __name__ == "__main__":
+    main()