feat: cleanup removal of old ssh plexer and logic

we also have added the necessary logic to auto prune ephemeral nodes because
headscale doesn't seem to automatically remove them. this change made use of a database
which is now stored in the persistent headplane directory.

drizzle/meta/_journal.json

@@ -0,0 +1,13 @@
+{
+	"version": "7",
+	"dialect": "sqlite",
+	"entries": [
+		{
+			"idx": 0,
+			"version": "6",
+			"when": 1750355487927,
+			"tag": "0000_spicy_bloodscream",
+			"breakpoints": true
+		}
+	]
+}