feat: add (incomplete) nix flake

dave.py isn't packaged yet. Will try to do this myself but dealing with
vcpkg is a bit annoying.

errornocord/tasks.py

@@ -0,0 +1,33 @@
+import asyncio
+import time
+from logging import debug, error
+
+import disnake
+
+from .state import client, idle_tracker, players
+
+
+async def cleanup():
+    debug("spawned cleanup thread")
+
+    while True:
+        await asyncio.sleep(3600)
+
+        targets = []
+        for guild_id, player in players.items():
+            if len(player.queue) == 0 and not player.current:
+                targets.append(guild_id)
+        for target in targets:
+            del players[target]
+        if len(targets):
+            debug(f"cleanup thread removed {len(targets)} empty players")
+
+        if (
+            not idle_tracker["is_idle"]
+            and time.time() - idle_tracker["last_used"] >= 3600
+        ):
+            try:
+                await client.change_presence(status=disnake.Status.idle)
+                idle_tracker["is_idle"] = True
+            except Exception as e:
+                error(f"failed to change status to idle: {e}")